LEME 


.  i  •     rt«irniu<' 

(HEMISTRY 


E  PER    Cdl/R  SE 


BohooT    Of 


LIBRARY 

OF   THE 

UNIVERSITY  OF  CALIFORNIA. 

OIKT  OK 

l  -C  -Heath  &CO-. 
331    Sansome   S't.  S.F.  Cal. 

Received 


Accession  No.  .       Class  No. 


BRIEFER    COURSE. 


ELEMENTS  OF  CHEMISTRY, 


DESCRIPTIVE  AND    QUALITATIVE. 


BY 


JAMES   H.   SHEPARD, 

ii 

PROFESSOR  OF  CHEMISTRY,  SOUTH  DAKOTA  AGRICULTURAL  COLLEGE,  AND 

CHEMIST  TO  THE  UNITED  STATES  EXPERIMENT 

STATION,  SOUTH  DAKOTA. 


W7B11SIT7 


BOSTON,   U.S.A.: 

D.  C.   HEATH  &  CO.,   PUBLISHERS. 

1895. 


Entered  according  to  Act  of  Congress,  in  the  year  1890,  by 

JAMES  H.  SHEPARD, 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


TYPOGRAPHY  BY  J.  S.  GUSHING  &  Co.,  BOSTON,  U.S.A. 
PKESSWOBK  BY  BERWICK  &  SMITH,  BOSTON,  U.S.A. 


PREFACE. 


THIS  briefer  course  follows,  in  general,  the  plan  of 
SheparcTs  Elements  of  Chemistry ;  but  the  reader  will 
notice  that  the  student  is  told,  to  a  still  less  extent 
than  in  the  larger  book,  what  he  may  expect  to  see 
while  working. 

Directions  for  preparing  reagents,  and  equipping  the 
laboratory,  and  discussions  of  methods  of  presentation 
are  not  given  here,  since  these  matters  are  fully  treated 
in  the  larger  book,  which  is  now  so  generally  used  that 
it  is  readily  accessible  to  all. 

The  subject-matter  of  this  text  is  so  arranged,  and 
the  experiments  are  so  simplified,  that  the  laboratory 
work  will  come  within  the  time  available  in  those 
schools  where  but  part  of  the  year  is  allotted  to  the 
study  of  chemistry.  The  text  will  also  be  found  accept- 
able in  many  schools  where  a  special  or  a  technical 
course  is  offered. 

Data  for  chemical  computations  given  at  the  begin- 
ning of  the  chapters,  numerous  exercises  for  review  or 
advanced  course,  a  close  adherence  to  inductive  methods, 
and,  wherever  possible,  careful  experimental  illustrations 

iii 


iv  PREFACE. 

of  all  important  facts  not  readily  understood  by  analogy, 
are  features  of  this  briefer  course  which  will,  it  is  hoped, 
commend  themselves  to  the  many  truly  scientific  educa- 
tors of  the  youth  in  all  parts  of  our  land. 

In  the  chapters  devoted  to  the  carbon  compounds,  owing 
to  the  unsatisfactory  results  usually  to  be  had  at  the  hands 
of  beginners  working  with  organic  substances,  it  seemed 
best  to  limit  the  work  to  the  preparation  and  discussion 
of  the  more  important  compounds  and  at  the  same  time 
dwelling  upon  the  general  laws  governing  the  origin  of 
the  derivatives  belonging  to  the  different  series. 

The  author  takes  pleasure  in  acknowledging  the  valu- 
able assistance  rendered  during  the  preparation  of  this 
work  by  Mr.  H.  Ellsworth  Call,  of  the  Des  Moines,  la., 
High  School ;  Miss  Ada  J.  Todd,  of  the  Bridgeport,  Conn., 
High  School ;  Mr.  H.  N.  Chute,  of  the  Ann  Arbor,  Mich., 
High  School ;  Prof.  I.  P.  Bishop,  State  Normal  and  Train- 
ing School,  Buffalo,  N.  Y. ;  Mr.  J.  T.  Draper,  Pueblo  High 
School,  Col. ;  and  by  many  other  prominent  educators  in 

all  parts  of  the  country. 

J.  H.  S. 
BROOKINGS,  March  30,  1891. 


co 


INTRODUCTION. 

PAGE 

ORIGIN  OP  CHEMISTRY.  —  Experimentation.  —  Solution.  —  Evapo- 
ration.—  Precipitation. —  Filtration. —  Decantation.  —  Reduction. 

—  Elements.  —  Table  of  the  Elements.  —  Atoms.  —  Symbols.  — 
Compounds.  —  Law  of  Definite  Proportions.  —  Dalton's  Atomic 
Theory.  —  Atomic  Weights. —  Molecules.  — Molecular  Formulae. 

—  Chemism  or  Chemical  Affinity.  —  Exercises       1-11 

CHAPTER  I. 

OXYGEN.  —  Data  for  Computations.  —  Occurrence.  —  Preparation 
and  Properties.  —  Crystallization.  —  Ozone.  —  Tests  for  Oxygen 
and  Ozone.  —  Exercises 12-18 

CHAPTER  H. 

HYDROGEN.  —  Data  for  Computations.  —  Occurrence.  —  Preparation 
and  Properties.  —  Water.  —  Occurrence.  —  Preparation  and  Prop- 
erties. —  Analysis  and  Synthesis  of  Water.  —  Solvent  Action  of 
'  Water.  —  Heat  Capacity  of  Water.  —  Exercises 19-28 

CHAPTER  m. 

NITROGEN.  —  Data  for  Computations.  —  Occurrence.  —  Preparation 
and  Properties.  —  Ammonia.  —  Occurrence.  —  Preparation  and 
Properties.  —  Tests  for  Ammonia.  —  Oxides  of  Nitrogen.  —  Nitro- 
gen Monoxide  :  its  occurrence,  properties,  and  tests.  —  Washing 
of  Gases.  —  Determination  of  Molecular  Weights.  —  Law  of 
Multiple  Proportions.  — Avogadro's  Hypothesis.  — The  Nitrogen 
Oxacids.  —  Nitric  Acid.  —  Occurrence,  etc.  —  Oxidizing  Re- 
agents. —  Exercises 29-42 

V 


VI  CONTENTS. 


CHAPTER   IV. 

PAGE 

THE  HALOGENS:  Data  for  Computations.  —  CHLORINE.  —  Occur- 
rence, etc.  —  Hydrochloric  Acid.  —  Occurrence,  etc. — A  Group 
Reagent.  —  Oxides  of  Chlorine.  —  The  Chlorine  Oxacids.  — 
BROMINE.  —  Occurrence,  etc.  —  The  Bromine  Acids.  —  IODINE. 

—  Occurrence,  etc.  —  The  Iodine  Acids.  —  FLUORINE.  —  Occur- 
rence, etc.  —  Hydrofluoric  Acid.  —  Exercises 43-56 

CHAPTER  V. 

BINARY  COMPOUNDS.  —  Higher  Compounds.  —  Acids.  —  Bases.  — 
Salts. — Normal,  Acid,  and  Basic  Salts. — Valence.  —  Substi- 
tuting Power  and  Valence.  —  Determination  of  Atomic  Weights 
by  Avogadro's  Hypothesis.  —  Exercises 57-64 

CHAPTER  VI. 

CARBON.  —  Data  for  Computations.  —  Occurrence,  etc.  —  Stone 
Coal.  —  Charcoal.  —  Graphite.  —  Diamonds.  —  Lignite.  —  Car- 
bon and  Hydrogen.  —  Methane.  —  Ethylene.  —  Acetylene.  — 
Carbon  and  Oxygen.  —  Carbon  Monoxide.  —  Carbon  Dioxide.  — 
Occurrence,  Properties,  etc.  —  Exercises 65-78 

CHAPTER   VII. 

SULPHUR,  SELENIUM,  AND  TELLURIUM.  —  Data  for  Computations. — 
SULPHUR.  —  Occurrence,  etc.  —  Hydrogen  Sulphide  •.  its  occur- 
rence, etc.  —  Oxides  of  Sulphur.  —  The  Sulphur  Oxacids.  —  Sul- 
phurous Acid :  its  occurrence,  etc.  —  Sulphuric  Acid  :  its  occur- 
rence, etc.  —  Nordhausen  or  Fuming  Sulphuric  Acid.  —  Test  for 
Thiosulphates.  —  Carbon  Disulphide.  —  SELENIUM  and  TELLU- 
RIUM.—  Exercises 79-91 

CHAPTER   VIII. 

SILICON:  its  occurrence,  etc.  —  Tests  for  the  Silicates.  —  BORON: 
its  occurrence,  etc.  —  Tests  for  Boric  Acid  and  its  Compounds. 

—  PHOSPHORUS:   its  occurrence,   eta — 33hosDhorus  and  Hydro- 
gen.— The   Pliospnorus   uxacias. — rnospnonc   ACIQ,    ana    its 
Tests,  —  Exercises  .  .  92-99 


CONTENTS.  Vll 


CHAPTER   IX. 

PAGE 

INTRODUCTORY  TO  THE  METALS.  —  Properties  of  the  Metals.  — 
Alloys.  —  Classification  of  the  Metals.  —  The  First  Group 
Metals.  —The  Second  Group  Metals.  —  The  Third  Group  Metals. 

—  The  Fourth  Group  Metals.  —  The  Fifth  Group  Metals  .    .    100-103 

CHAPTER  X. 

THE  FIRST  GROUP  METALS.  —  Data  for  Computations.  —  LEAD. — 
Occurrence  and  Preparation.  —  Properties  and  Compounds.  — 
Tests  for  Lead.  —  SILVER.  —  Occurrence  and  Preparation.  —  Prop- 
erties and  Compounds.  —  Tests  for  Silver.  —  MERCURY.  —  Oc- 
currence, etc.  —  Separation  and  Identification  of  Lead,  Silver, 
and  Mercury.  —  Exercises 104-113 

CHAPTER  XI. 

THE  SECOND  GROUP  METALS.  —  Data  for  Computations.  —  ARSENIC. 

—  Occurrence  and  Preparation.  —  Properties  and  Compounds.  — 
Tests  for  Arsenic.  —  ANTIMONY.  —  Occurrence  and  Preparation. 

—  Properties  and  Compounds.  —  Tests  for  Antimony.  —  TIN.  — 
Occurrence,     etc.  —  BISMUTH.  —  Occurrence,    etc.  —  COPPER.  — 
Occurrence,  etc.  —  CADMIUM.  —  Occurrence,  etc.  —  Analysis  of 

the  Second  Group  Metals.  — Exercises 114-130 

CHAPTER  XH. 

THE  THIRD  GROUP  METALS. — Data  for  Computations.  —  IRON. — 
Occurrence  and  Preparation.  —  Steel.  —  Properties  and  Com- 
pounds of  Iron.  —  Tests  for  Iron.  —  Tests  for  Ferro-  and  Ferri- 
Cyanic  Acids.  —  CHROMIUM.  —  Occurrence,  etc.  —  ALUMINIUM. 

—  Occurrence,    etc.  —  NICKEL.  —  Occurrence,  etc.  —  COBALT.  — 
Occurrence,   etc.  —  MANGANESE.  —  Occurrence,    etc.  —  ZINC.  — 
Occurrence,  etc.  —  Analysis  of  the  Third  Group  Metals.  —  Exer- 
cises      131-147 

CHAPTER   Xni. 

THE  FOURTH  GROUP  METALS.  —  Data  for  Computations.  —  BARIUM. 

—  Occurrence  and  Preparation.  —  Properties  and  Compounds. — 
Tests.  —  STRONTIUM.  —  Occurrence,    etc.  —  CALCIUM.  —  Occur- 
rence, etc.  —  MAGNESIUM.  —  Occurrence,  etc.  —  Analysis  of  the 
Fourth  Group  Metals.  —  Exercises 148-155 


yiii  CONTENTS. 

CHAPTER   XIV. 

PAGE 

THE  FIFTH  GROUP  METALS.  —  Data  for  Computations.  —  POTASSIUM. 

—  Occurrence  and  Preparations.  —  Properties  and  Compounds.  — 
Test.  —  SODIUM.  —  Occurrence,    etc.  —  AMMONIUM.  —  ANALYSIS 
OF  AN  UNKNOWN  SUBSTANCE.  —  Solution.  —  Detection  of  Bases. 

—  Detection  of  Acids 156-167 

CHAPTER   XV. 

INTRODUCTORY  TO  THE  CARBON  COMPOUNDS.  —  Organic  and  Inor- 
ganic Substances.  —  Homology.  —  Table  of  the  Hydrocarbon 
Series.  —  Names  of  the  Members  of  the  Hydrocarbon  Series.  — 
Elementals  and  Derivatives.  —  Substitution.  —  Addition  Prod- 
ucts. —  Unsaturated  Radicals  of  the  Paraffin  Series.  —  Isomerism. 

—  Uniformity  among  Derivatives 168-175 

CHAPTER  XVI. 

THE  PARAFFIN  SERIES,  CnH2n+2. —  Occurrence  and  Preparation. — 
Properties.  —  METHANE  AND  ITS  DERIVATIVES.  —  I.  HALOGEN 
DERIVATIVES. — Chlor-Methane,  or  Methyl  Chloride. — Trichor- 
Methane,  or  Chloroform.  —  Tri-iodo-Methane,  or  lodoform. — 
OXYGEN  DERIVATIVES.  —  Methyl  Alcohol,  or  Wood  Alcohol.  — 
Methyl  Ether.  —  Methyl  Aldehyde,  or  Formic  Aldehyde.  —  For- 
mic Acid.  —  NITROGEN  DERIVATIVES.  —  The  Methylamines. — 
Cyanogen  and  Hydrocyanic  Acid.— Nitro-Methane. —DERIVA- 
TIVES WITH  SULPHUR,  ARSENIC,  PHOSPHORUS,  etc.  —  The  Mercap- 
tans,  Phosphines,  Arsines,  and  Stibines.  —  METALLIC  DERIVA- 
TIVES.—  ETHANE  AND  ITS  DERIVATIVES.  —  OXYGEN  DERIVATIVES. 
-Ethyl  Alcohol.  — Ethyl  Ether.  — Ethyl  Aldehyde.  —  Acetic 
Acid,  Soap,  Ethyl  Nitrate 176-200 

CHAPTER   XVII. 

THE.  OLEFINE  DERIVATIVES.  —  Ethylene.  —  Lactic  Acid.  —  Oxalic 
Acid.  —  Succinic  Salt.  —  Malic  Acid.  —  Tartaric  Acid.  —  Citric 
Acid.  —  Glycerine,  Glycerol,  or  Propenyl  Alcohol.  —  Oleic  Acid. 

—  ACETYLENE    DERIVATIVES. — Linoleic    Acid.  —  Mannite,    or 
Manitol  .  .   201-207 


CONTENTS.  IX 

CHAPTER   XVIII. 

PACK 

THE  CARBOHYDRATES.  —  THE  SUCROSES.  —  Milk  Sugar,  Lactose.  — 
THE  GLUCOSES.  —  Grape  Sugar,  Dextrose,  or  Glucose. — THE 
AMYLOSES.  —  Starch,  or  Amylum.  —  The  Gums.  —  Cellulose. — 
Gun-Cotton.  —  The  Glucosides 208-217 

CHAPTER   XIX. 

THE  TERPENES. — THE  BENZENES.  —  Benzene.  —  Phenol,  Phenyl 
Alcohol,  or  Carbolic  Acid.  —  Resorcin,  and  Pyragallol.  —  Nitro- 
benzene. —  Aniline,  Amidobenzeiie,  or  Phenylamine.  —  The  Tol- 
uenes.—  THE  STYRENES,  OR  CINNAMINES. —  THE  NAPHTHALENES. 
—  THE  ANTHRACENES 218-227 

CHAPTER   XX. 
THE  ALKALOIDS  AND  THE  ALBUMINOIDS  .  .   228-230 


TH* 

TJHI7BRSIT7 


INTRODUCTION 


1.  Origin  of  Chemistry.  —  The  rudiments  of  the  science 
of  Chemistry  may  be  traced  back  to  the  ancient  Egyptians. 

About  640  A.D.  the  Arabs  invaded  Egypt,  where  they 
obtained  a  knowledge  of  the  sciences  practised  there.  Dur- 
ing the  Middle  Ages  they  preserved  this  knowledge,  and 
from  their  academies  in  Spain  as  centres,  it  gradually  spread 
over  all  parts  of  the  civilized  world.  Up  to  this  time  the 
main  inducement  for  studying  and  practising  chemistry 
was  a  hope  of  discovering  the  Philosopher's  Stone,  a  stone 
that  should  change  the  baser  metals  into  gold.  During 
these  researches  many  important  facts  in  inorganic  chem- 
istry were  discovered. 

From  the  fifteenth  to  the  seventeenth  century  the  Elixir 
Vitce,  or  Elixir  of  Life,  a  cordial  that  should  cure  all  the 
ills  of  mankind  and  give  perpetual  youth,  was  the  chief 
object  sought.  In  this  search  many  valuable  medicines 
were  discovered. 

During  the  seventeenth  century  the  properties  of  gases 
were  investigated,  and  in  both  this  and  the  succeeding 
century  other  important  advances  were  made. 

Notwithstanding  all  previous  advancement,  however,  the 
modern  science  of  Chemistry  is  emphatically  a  product  of 
the  present  century. 

2.  Experimentation.  —  The  greatest  hindrance  to  chemical 
progress  in  the  past  lay  in  the  fact  that  the  science  of  ex- 

1 


INTRODUCTION. 


perimenting  was  not  well  understood.  Erroneous  theories 
were  advanced  and  believed  in  for  centuries.  These  theo- 
ries were  finally  overthrown  by  the  rigid  test  of  experiment, 
and  thus  progress  and  improvement  were  made  possible. 

When  we  experiment  with  a  substance,  we  so  treat  it  that 
we  may  ascertain  its  properties  and  behavior. 

In  experimenting  with  substances,  the  chemist  finds  fre- 
quent .use  for  such  processes  as  Solution,  Evaporation, 
Precipitation,  Filtration,  Decantation,  Reduction,  Distilla- 
tion, and  Electrolysis.  Excepting  the  two  latter,  which 
will  be  explained  hereafter,  these  processes  may  be  illus- 
trated by  experiments. 

3.  Solution,  —  EXPERIMENT  1.  Place  about  a  gram  of  com- 
mon salt  (Nad)  in  a  test-tube,  and  then  fill  the  test-tube  half 
full  of  water.  Now  gently  heat  the  tube 
in  the  Bunsen  flame  (Fig.  1)  ;  frequently 
cover  the  mouth  of  the  tube  with  the  thumb 
and  shake. 

EXERCISE.  What  becomes  of  the  salt  ?  Define 
the  process  called  "  solution."  What  is  a  solu- 
tion ?  Define  solids  ;  liquids ;  gases. 


4.  Evaporation,  —  EXP.  2.  Place  a  few 
drops  of  the  salt  solution  obtained  in  Exp. 
1  on  a  piece  of  tin  or  in  an  iron  spoon. 
Now  warm  gently  till  the  water  has  disap- 
peared. 


FIG-  1. 


Ex.  What  became  of  the  water  ?  What  remains  on  the  tin  ?  Define 
evaporation.  What  is  the  object  of  evaporation  ? 

5.  Precipitation.  —  EXP.  3.  To  about  one-half  of  the  salt 
solution  (Exp.  1)  add  nearly  an  equal  volume  of  a  solution  of 
silver  nitrate  (AgNO3). 


INTRODUCTION. 


3 


FIG.  2. 


Ex.  What  takes  place  ?  (The  silver  of  the  silver  nitrate  has  united 
with  the  chlorine  of  the  common  salt  to  form  the  solid  silver  chloride, 
AgCl,  thus  removing  the  chlorine  from  the  salt  solution,  or  the  silver 
from  the  silver  nitrate  solution.)  What  is  the  object  of  precipitation  ? 
Why  would  not  evaporation  do  instead  ?  Define  precipitation ;  precip- 
itate. 

6.  Filtration.  —  EXP.  4.      Support  a  funnel 
on  a  ring-stand,  and  place  a  beaker  underneath 
the    funnel ;    fold    a    round    filter-paper  twice 

"(Fig.  2),  making  the  folds  at  right  angles  to 
each  other ;  place  the  point  of  the  paper  in  the 
funnel,  and  open  one  of  the  pockets  formed  by 
folding  the  paper :  into  this  pocket  pour  the 
contents  of  the  tube  used  in  Exp.  3. 

Ex.  What  occurs  ?  What  is  the  object  of  nitration  ?  Would  evapo- 
ration have  answered  as  well  ?  Try  it.  Define  filtration  ;  filtrate.  How 
can  you  wash  the  precipitate  while  it  is  on  the  filter-paper  ? 

7.  Decantation.  —  EXP.  5.    Precipitate  the  remainder  of  the 
salt  solution  (Exp.  1)  with  silver  nitrate ;  warm  gently,  and 
allow  the  tube  to  stand  for  a  few  minutes.     Now  pour  off  the 
solution,  leaving  the  solid  precipitate  in  the  tube. 

Ex.  What  have  you  '  accomplished  ? 
Define  decantation.  How  can  you  wash 
a  precipitate  by  decantation  ?  Compare 
decantation  with  filtration. 

8.  Reduction.  —  EXP.  6.     Into  a 
piece  of  charcoal  bore  a  hole  with 
the  point  of  a  penknife,  and  in  this 
hole  place  the  precipitate  obtained 
in  Exps.  4   or   5.     Now  heat  this 
precipitate  in  the  blow-pipe  flame 
(Fig.  3). 

Ex.  What  is  the  bead  you  thus  obtain  ?  What  became  of  the  chlo- 
rein?  What  does  *  *  reduction ' '  mean  ? 


FIG.  3. 


4  INTRODUCTION. 

9.  Elements,  —  In  the  last  experiment  silver  was  obtained 
from  a  substance  that  did  not  at  all  resemble  silver.  In 
fact,  silver  was  reduced  from  its  chlorine  compound.  Chem- 
ists have  found,  however,  that  neither  the  silver  nor  the 
chlorine  can  be  further  divided;  hence  these  substances 
are  called  elements. 

DEFINITION.  A  chemical  element  is  a  substance  that  cannot  be  divided, 
or  at  least  has  not  been  divided,  into  simpler  substances. 

At  the  present  time  about  seventy  different  elements  are 
known.  Of  course  it  has  not  been  possible  to  examine 
every  portion  of  the  earth's  crust  for  elements,  but  such 
elements  as  are  now  discovered  from  time  to  time  occur 
only  in  very  small  quantities. 

Again,  it  is  possible  that  some  substances  now  known  to 
us  as  elements  may  prove  to  be  compounds  as  our  appli- 
ances for  chemical  investigation  are  improved. 

The  following  table  gives  a  list  of  the  elements.  The 
first  column  contains  the  names  of  the  elements ;  the  signi- 
fication of  the  other  columns  will  be  explained  further  on. 


INTRODUCTION. 


10,   A  Table  of  the  Elements. 


Names. 

Symbols. 

Atomic 
Weights. 

Physical 
condition  at 
ordinary 
temperature. 

Specific  Gravity. 

Aluminum 

Al"" 

27. 

Solid 

2.60 

Antimony 

Sb'"-v 

120. 

u 

6.71 

Arsenic 

As'"-v 

75. 

« 

5.73 

Barium 

Ba" 

137. 

(C 

3.75 

Beryllium 

Be" 

9. 

(« 

2.07 

Bismuth 

Bi'".v 

208. 

11 

9.80 

Boron 

B'" 

11. 

n 

2.5? 

Bromine 

Br''v 

80. 

Liquid 

3.187 

Cadmium 

Cd" 

112. 

Solid 

8.60 

Caesium 

Cs' 

133. 

K 

1.88 

Calcium 

Ca" 

40. 

u 

1.57 

Carbon 

C"" 

12. 

<( 

3.5-.6 

Cerium 

Ce'"'"" 

141. 

« 

6.68 

Chlorine 

Cl'-v 

35.5 

Gas 

2.450 

Chromium 

Cr""-vi 

52. 

Solid 

6.50 

Cobalt 

Co"-"" 

59. 

ti 

8.5-.7 

Copper 

Cu" 

63.3 

it 

8.95 

Didymium 

D"f 

142.3 

a 

6.54 

Erbium 

E'" 

166. 

u 

— 

Fluorine 

F' 

19. 

Gas 

1.313 

Gallium 

G"" 

69. 

Solid 

5.95 

Gold 

Au''"' 

196.5 

a 

19.32 

Hydrogen 

H' 

1. 

Gas 

0.069 

Indium 

In"" 

113.6 

Solid 

7.42 

Iodine 

I'-v 

127. 

« 

4.948 

Iridium 

jrM,  nn,\i 

193. 

n 

22.42 

Iron 

Fe","",vi 

56. 

(C 

7.86 

Lanthanum 

La"' 

138.2 

(( 

6.10 

Lead 

Pb"'  "" 

207. 

(( 

11.37 

Lithium 

Li' 

7. 

(( 

0.59 

Magnesium 

Mg".'"'.™ 

24. 

tc 

1.74 

Manganese 

Mn" 

55. 

(( 

8.03 

Mercury 

Hg" 

200. 

Liquid 

13.55 

Molybdenum 

Mo"-  ""'vi 

96. 

Solid 

8.60 

Nickel 

Ni","" 

58. 

K 

8.90 

ars*V 
INTRODUCTIONS 


Names. 

Symbols. 

Atomic 
Weights. 

Physical 
condition  at 
ordinary 
temperature. 

Specific  Gravity. 

Niobium 

Nbv 

94. 

Solid 

7.06 

Nitrogen 

N'ff,v 

14. 

Gas 

0.971 

Osmium 

Os".""'vi 

199. 

Solid 

22.48 

Oxygen 

O" 

16. 

Gas 

1.105 

Palladium 

Pd"'"" 

106. 

Solid 

11.40 

Phosphorus 

-pi,  til,  v 

31. 

-"  ! 

Colorless  1.83 
Red  2.20 

Platinum 

Ptrr,  nn 

195. 

(C 

21.50 

Potassium 

K' 

39. 

ti 

0.87 

Rhodium 

Ro"'""'vi 

104. 

« 

12.10 

Rubidium 

Rb' 

85. 

u 

1.52 

Ruthenium 

RufU"f,Ti 

103.5 

(( 

12.26 

Samarium 

Sm 

150. 

It 

— 

Scandium 

Sc 

44. 

It 

— 

Selenium 

Se"-""«vi 

79. 

u 

4.50 

Silicon 

Si"" 

28. 

(( 

2.39 

Silver 

Ag' 

108. 

u 

10.53 

Sodium 

Na' 

23. 

1  1 

0.978 

Strontium 

Sr" 

87.5 

u 

2.54 

Sulphur 

$n,ttn,vi 

32. 

(( 

2.05 

Tantalum 

Tav 

182. 

u 

10.40 

Tellurium 

Te"'"">vi 

125.? 

C  (, 

6.40 

Terbium 

Tb 

148.5? 

l.t 

— 

Thallium 

Xl'-'" 

204, 

tl 

11.85 

Thorium 

Th"" 

232. 

it 

11.00 

Tin 

Sn"«"" 

118. 

It 

7.29 

Titanium 

T^"'  "" 

48. 

(( 

— 

Tungsten 

W/f,vi 

184. 

(( 

19.12 

Uranium 

U'"f»vi 

239.8 

(  i 

18.70 

Vanadium 

V'/'»  v 

51.5 

u 

5.50 

Ytterbium 

Yb 

173. 

u 

— 

Yttrium 

Y"' 

89. 

u 

— 

Zinc 

Zn" 

65. 

u 

7.15 

Zirconium 

Zr"" 

90. 

l« 

4.15 

INTRODUCTION. 


11.  Atoms. — It  is  the  prevailing  belief  that  matter  is 
made  up  of  extremely  minute,  indivisible  particles  called 
atoms.     Many  reasons  lead  to  the  conclusion  that  all  the 
atoms  of  the  same  element  are  alike,  but  that  they  are 
unlike  the  atoms  of  any  other  element. 

12.  Symbols.  —  It  is  often  convenient  to  represent  the 
name  of  an  element  by  some  letter  or  letters,  as  H  for 
hydrogen,    O    for   oxygen,    Cd    for    cadmium,    etc.      In 
the  second  column  of  the  table  (Art.  10)  are  given  the 
symbols  commonly  employed.      These   symbols   are   also 
used  for  other  purposes,  thus :  H  also  stands  for  an  atom 
of  hydrogen,  O  for  an  atom  of  oxygen,  etc.     When  we 
wish  to  represent  more  than  one  atom,  figures  are  used, 
thus :    2  H   means   two   atoms   of  hydrogen ;    3  H,   three 
atoms ;  etc.     Subscript  figures  are  used  for  the  same  pur- 
pose when  more  than  one  symbol  is  needed  to  represent 
certain  substances;  thus:    H2O,   water;   NH3,   ammonia; 
C2H4,  ethylene ;  etc. 

Some  elements  have  symbols  derived  from  their  Latin 
names.  This  is  perplexing  to  the  student,  but  this  list 
will  explain :  — 


Antimony,  Sb,  from  Stibium. 
Copper,  Cu,  "  Cuprum. 
Gold,  Au,  u  Aurum. 

Iron,  Fe,     "     Ferrum. 

Lead,  Pb,    "     Plumbum. 

Mercury,     Hg,    "      Hydrargyrum. 


Potassium,  K,    from  Kalium. 
Silver,  Ag,     "     Argentum. 

Sodium,        Na,     "     Natrium. 
Tin,  Sn,     "     Stannum. 

Tungsten,     W,      "     Wolframium. 


NOTE.  At  the  right  of  the  symbols  in  the  table  the  indices  and  numer- 
als are  used  to  indicate  the  valence  (Art.  76)  of  the  elements.  The 
symbols  are  commonly  written  without  these. 

13.  Compounds.  —  EXP.  7.  Mix  thoroughly  0.56*  very  fine 
jron  filings  and  0.32s  flowers  of  sulphur.  Place  this  mixture 


8  INTRODUCTION. 

in  an  iron  spoon,  and  heat  it  to  redness  in  the  Bunsen  flame. 
The  iron  and  sulphur  combine,  forming  the  chemical  compound, 
ferrous  sulphide  (FeS). 

Ex.  Define  a  chemical  compound.  Compare  the  ferrous  sulphide  with 
the  iron  and  sulphur  of  which  it  is  composed. 

14,  Law  of  Definite  Proportions,  —  When  elements  unite, 
as  in  the  case  of  iron  and  sulphur,  it  has  been  proven  that 
they  always  unite  in  fixed  and  definite  proportions.     For 
example :  56  parts,  by  weight,  of  iron  always  unite  with 
32  parts  of  sulphur,  to  form  ferrous  sulphide  (FeS).  Again : 
23  parts  of  sodium  always  unite  with  35.5  parts  of  chlorine 
to  form  common  salt  (NaCl),  etc.     The  law  may  be  stated 
in  this  form :  — 

Any  given  chemical  compound  always  contains  the  same 
elements  in  the  same  proportions  by  weight. 

15,  Atomic  Theory,  —  To  account  for  the  union  of  ele- 
ments in  definite  proportions  by  weight,  the  supposition 
has  been  made  that  the  atoms  of  the  elements  are  the  units 
between  which  the  union  takes  place. 

The  simplest  case  is  where  one  atom  of  one  element 
unites  with  one  atom  of  another,  as  in  common  salt 
(NaCl),  where  one  atom  of  sodium  unites  with  one  atom 
of  chlorine.  The  next  case  is  where  two  atoms  of  one  ele- 
ment unite  with  one  atom  of  another,  as  in  water  (H2O), 
where  two  atoms  of  hydrogen  unite  with  one  of  oxygen. 
Other  relations  also  exist  with  which  the  student  will  soon 
become  familiar. 

16,  Atomic  Weights.  —  It  is  evident  that,  however  small 
atoms  may  be,  they  must  still  have  some  weight.     It  is 
true  that  the  weight  of  the  heaviest  atom  is  so  slight  that 


INTEODUCTWMj^  '    -flVV   ^ 

it  could  not  be  determined  by  the  mo^^fSsffieDalance 
ever  constructed,  but  it  is  also  true  that  it  is  not  neces- 
sary to  know  the  absolute  weights  of  the  atoms.  If  we  can 
determine  their  relative  weights,  all  purposes  will  be  suffi- 
ciently answered :  and  this  has  been  done.  For  this  pur- 
pose the  hydrogen  atom  has  been  taken  as  unity,  and  the 
relative  weights  of  the  atoms  of  the  other  elements,  as 
compared  with  the  hydrogen  atom,  have  been  determined. 
How  this  has  been  accomplished  will  be  explained  here- 
after ;  for  the  present  it  must  suffice  to  say  that  the  atom 
of  oxygen  has  been  estimated  to  be  16  times  as  heavy  as 
the  hydrogen  atom,  the  atom  of  iron  56  times  as  heavy, 
and  the  atom  of  mercury  200  times  as  heavy ;  and  so,  like- 
wise, certain  numbers  have  been  assigned  to  the  atoms  of 
all  the  known  elements.  Now,  these  numbers  are  called 
the  atomic  weights  of  the  elements. 

Moreover,  since  these  numbers  fix  the  ratios  in  which 
the  elements  combine,  they  are  also  called  Combining 
Numbers  ;  e.g.  56  and  32  are  respectively  the  combining 
numbers  of  iron  and  sulphur.  The  atomic  weights  now 
assigned  to  the  elements  are  given  in  the  third  column  of 
Art.  10. 

17.  Molecules. — We  have  already  learned  (Exp.  3)  that 
the  atoms  of  silver  unite  with  the  atoms  of  chlorine  to  form 
silver  chloride.  If  we  consider  a  quantity  of  silver  chloride 
containing  but  one  atom  each  of  silver  and  chlorine,  it  is 
evident  that  no  smaller  quantity  of  silver  chloride  could 
exist,  since  the  atoms  themselves  are  indivisible ;  and  if 
we  take  away,  for  example,  the  atom  of  chlorine,  free  silver 
is  obtained  (Exp.  6).  To  such  a  smallest  possible  quantity 
of  a  chemical  compound  that  can  exist  as  such  the  term 
Molecule  is  applied. 


10  INTRODUCTION. 

18.  Molecular  Formulae.  —  In  representing  the  molecules 
of  compound  bodies,  the  symbols  of  the  elements  composing 
those  bodies  are  written  side  by  side,  thus :  silver  nitrate, 
AgNO3;  sulphuric  acid,  H2SO4;  potassium  nitrate,  KNO3; 
etc.     If  we  wish  to  write  any  number  of  molecules  of  a 
substance,  figures  are  used :    thus,    3  KNO3  means  three 
molecules  of  potassium  nitrate ;   2  H2O,  two  molecules  of 
water;  etc. 

In  the  case  of  the  molecules  of  the  elements  it  is  cus- 
tomary to  write  the  number  of  atoms  in  the  molecule  by 
means  of  a  subscript  figure  :  thus,  H2,  O2,  N2,  etc.,  represent 
molecules. 

NOTE.  It  has  been  a  very  difficult  task  to  determine  the  molecular  for- 
mulae of  the  compounds.  How  this  may  be  done  will  be  explained  in  a 
subsequent  chapter. 

Ex.  Determine  the  number  of  oxygen  atoms  represented  in  the  fol- 
lowing :  3  H2S04  ;  8  HN03 ;  16  K2Cr2O7 ;  24  H20  ;  5  Ca(N03)2. 

19.  Chemism,  or  Chemical  Affinity.  —  The  force  causing 
atoms  to   unite  with   one   another  to  form   molecules   is 
called  Chemism.     Between  the  atoms  of  any  two  elements 
this  force  is  always  a  constant  quantity ;  but  it  varies  for 
the  atoms  of  any  other  element  when  taken  with  either  of 
these  two  elements. 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  Attach  threads  to  the  four  corners  of  a  small  square  of  wire  gauze, 
and  then  place  on  the  gauze  a  crystal  of  copper  sulphate,  CuSO4.     Now 
suspend  the  crystal  on  the  gauze  in  a  beaker  of  water.    Note  the  phenom- 
enon of  solution. 

2.  Will  alcohol  dissolve  in  water  ?    Will  sulphuric  acid  ?     Will  oil  ? 
Will  camphor  gum  dissolve  in  water  ?  in  alcohol  ?    What  will  dissolve 
rubber  gum  ? 

3.  Place  a  beaker  of  fresh  well-water  in  a  warm  place,  and  allow  it  to 
remain  quiet  for  some  time.     What  collects  on  the  sides  of  the  glass  ?    Is 


INTRODUCTION.  11 

air  soluble  in  water  ?    Is  ammonia  gas  ?    Name  some  other  gases  that 
are  soluble  in  water. 

4.  Define  a  solvent ;  a  menstruum  ;  a  tincture  ;  a  fluid  extract ;  a  sat- 
urated solution ;  a  dilute  solution. 

5.  Carefully  weigh  an  evaporating- dish,  and  then  place  in  it  exactly 
0.65s  zinc.     Place  the  evaporating-dish  on  the  sand-bath,  and  cover  the 
zinc  with  hydrochloric  acid,  HC1.     Heat  the  sand-bath  gently,  and  add 
more  hydrochloric  acid,  if  necessary,  till  the  zinc  is  all  dissolved.     You 
thus  obtain  a  solution  of  zinc  chloride,  ZnCl2.     Now  carefully  evaporate 
this  solution  to   dryness,  and  then  place  the  evaporating-dish  under  a 
small  bell-glass  till  the  dish  and  its  contents  are  cool.     Rapidly  weigh  the 
dish  and  its  contents,  and  from  this  weight  subtract  the  weight  of  the  dish. 
This  gives  the  weight  of  the  zinc  chloride.    From  this  last  weight  subtract 
the  weight  of  the  zinc,  and  thus  obtain  the  weight  of  the  chlorine  that 
united  with  the  zinc. 

From  the  formula  ZnCl2  it  appears  that  0.71  parts  of  chlorine  should 
unite  with  0.65  parts  of  zinc ;  hence  the  zinc  chloride  should  weigh 
0.65s  +  0.71g=  1.36s.  What  does  this  experiment  show  ? 

NOTE.  Owing  to  experimental  errors  and  to  the  influence  of  moisture, 
these  results  will  only  be  approximated. 

6.  Moisten  with  water  a  pine  splinter  or  a  partly  burned  match,  and 
dip  it  into  dry  powdered  sodium  carbonate,  NajCO3.     Heat  the  match  in 
the  Bunsen  flame  till  dry  and  charred.     If  the  match  be  not  coated  with 
the  carbonate,  moisten,  and  proceed  as  before.     With  the  warm  match 
take  up  a  small  bit  of  silver  chloride  (Exp.  3),  which  is  to  be  heated  hi 
the  Bunsen  flame. 

Do  you  thus  obtain  a  bead  ?  Compare  with  Exp.  6.  Try  in  this  way 
some  compounds  of  lead  and  copper. 


CHAPTER   I. 

OXYGEN. 

DATA  FOR  COMPUTATIONS.  —  Symbol,  O  ;  Molecular  Formula,  O2 ;  Atomic 
Weight,  10  ;  Specific  Gravity,  1.1056  ;  Weight  of  I1  at  0°  C.  and  160™m, 
1.430*. 

20,  Occurrence.  —  Oxygen  is  the  most  abundant  of  all 
the  elements.     It  occurs  free  in  the  atmosphere,  of  which 
it  constitutes  about  23  per  cent  by  weight.     In  its  com- 
pounds oxygen  occurs  most  plentifully,  since  from  44  to 
48  per  cent  by  weight  of  the  earth's  crust,  and  88  to  89  per 
cent  by  weight  of  water,  consists  of  oxygen.    Every  element 
except  fluorine  unites  with  oxygen  to"  form  compounds. 

21,  Preparation  and  Properties.  —  Since  oxygen  occurs  free 
in  the  atmosphere,  we  have  all  had  some  experience  with 
it  in  that  form.    As  it  thus  occurs  it  is  largely  diluted  with 
nitrogen  and  other  gases.     Notwithstanding  our  familiarity 
with  atmospheric  oxygen,  it  will  be  well,  in  this  connection, 
to  make  one  or  two  experiments. 

EXP.  8.  Ignite  a  common  match,  and  when  burning  freely 
hold  the  tip  upward.  Note  the  flame,  and  how  the  match  is 
consumed.  When  a  portion  of  the  match  is  charred,  extinguish 
the  flame,  and  note  the  behavior  of  the  glowing  coal  which 
remains. 

EXP.  9.  Cease  breathing  for  about  fifteen  seconds,  and  note 
the  effect  upon  the  system. 

Ex.     When  the  flame  is  extinguished,  does  the  match  still  continue  to 
waste  away  ?     How  does  the  flame  differ  from  the  slow  burning  of  the 
12 


OXYGEN.  13 

coal  ?  What  remains  after  the  charcoal  has  burned  away  ?  Is  wood  an 
element  or  a  compound  ?  For  how  long  a  time  would  it  be  safe  to  "  hold 
the  breath  "  ?  Define  suffocation  ;  strangulation  ;  asphyxiation. 

The  two  great  uses  of  free  atmospheric  oxygen  are  to 
support  respiration  and  combustion. 

All  animals  consume  free  oxygen  during  respiration. 
In  the  case  of  air-breathing  animals  the  blood,  while 
passing  through  the  lungs,  is  thoroughly  brought  into 
contact  with  the  air ;  and  thus  is  the  blood  purified.  In 
water-breathing  animals,  like  fishes,  gills  take  the  place  of 
lungs ;  while  in  the  still  lower  orders,  pores  and  spiracles, 
distributed  over  the  surface  of  the  body,  serve  a  like  purpose. 

When  we  say  a  body  burns,  it  is  equivalent  to  saying  that 
it  unites  with  oxygen.  In  fact,  when  wood,  coal,  gas,  oils, 
etc.,  are  burning,  these  substances  are  entering  into  chem- 
ical combination  with  the  oxygen  of  the  air.  A  flame  is  a 
burning  gas ;  hence  solids  must  be  heated  to  a  temperature 
(the  kindling-point)  high  enough  to  convert  them  into 
gases  before  flames  are  produced.  Substances  may  oxidize 
or  burn  at  high  or  low  temperatures.  When  flames  are 
produced,  the  temperature  is  high ;  but  when  iron  is  rust- 
ing, or  wood  rotting,  or  oxygen  combining  with  the  im- 
purities of  the  blood,  the  temperature  is  low.  It  matters 
not,  however,  at  what  temperature  the  oxidation  may  oc- 
cur ;  a  given  weight  of  a  substance,  when  oxidized,  always 
produces  the  same  quantity  of  heat. 

Ex.  Define  combustion  ;  oxidation.  Why  can  a  lump  of  coal  not  be 
ignited  by  means  of  a  match?  Explain  the  philosophy  of  ''kindling- 
wood."  Why  does  blowing  a  fire  hasten  combustion,  while  the  same 
treatment  would  extinguish  a  candle  flame  ?  Explain  the  use  of  chim- 
neys, drafts,  and  dampers  in  stoves  and  furnaces. 

Pure  oxygen  varies  much  from  the  diluted  gas  in  the 
phenomena  which  it  exhibits  during  combustion.  There 


14  OXYGEN. 

are  several  ways  of  preparing  pure  oxygen,  but  trie  best 
ones  are  by  decomposing  its  compounds,  such  as  red  oxide 
of  mercury  or  mercuric  oxide,  HgO,  and  potassium  chlo- 
rate, KClOo,  by  means  of  heat. 

EXP.  10.  Place  a  small  quantity  of  mercuric  oxide  in  a  test- 
tube.  Heat  the  test-tube  just  under  the  oxide  in  the  Bunsen 
flame  for  a  short  time,  frequently  inserting  a  glowing  match. 

Ex.  Compare  with  Exp.  8.  What  collects  on  the  sides  of  the  tube  ? 
Into  what  substances  has  the  oxide  of  mercury  been  separated  ?  Has 
oxygen  an  odor  ?  any  color  ?  Why  are  these  two  latter  facts  wise 
provisions  ? 

This  method  of  preparing  oxygen  would  be  too  expensive 
when  large  quantities  of  that  gas  are  needed  for  laboratory 
purposes.  In  the  latter  case  potassium  chlorate  is  used. 
In  order  to  have  the  gas  liberated  at  as  low  a  temperature 
as  possible,  one-fourth  part,  by  weight,  of  black  oxide  of 
manganese  or  manganese  dioxide,  MnO2,  is  mixed  with 
the  potassium  chlorate.  The  manganese  dioxide  under- 
goes no  change,  but  the  potassium  chlorate  is  reduced  to 
potassium  chloride,  KC1. 

EXP.  11.  Place  a  small  quantity  of  this  mixture  in  a  test- 
tube,  and  proceed  as  in  Exp.  10.  Compare  the  results  with 
that  experiment. 

EXP.  12.  Place  (say)  100g  potassium  chlorate  and  25g  man- 
ganese dioxide  in  an  oxygen  generator.  Be  sure  that  the 
chemicals  are  pure.  Heat  carefully,  and  collect  the  gas  in 
gas-bags  or  in  jars  over  the  pneumatic  trough,  or  in  gas- 
holders. Now  prepare  the  materials  for  the  following  exper- 
iments, which  are  best  shown  in  a  darkened  room. 

EXP.  13.  Make  a  pencil  of  bark  charcoal,  and  tie  around 
it  an  iron  wire.  Ignite  the  charcoal,  and  by  means  of  the 
wire  lower  it  into  a  jar  of  oxygen.  Note  the  scintillations. 


OXYGEN. 


15 


EXP.  14.  Draw  the  temper  from  a  watch-spring  by  heating 
it  in  the  Bunsen  flame,  and  uncoil  it.  File  one  end  thin,  and 
bend  it  into  a  loop.  Now  heat  the  loop,  and  make  a  sulphur 
tip  for  the  spring  by  dipping  the  heated  loop  into  flowers  of 
sulphur.  Ignite  the  sulphur,  and  carefully  place  the  spring 
in  a  jar  of  oxygen.  Note 
the  sulphur  flame  and  the 
combustion  of  the  spring 
(Fig.  4). 

EXP.  15.  Make  a  small 
pencil  by  twisting  together 
fine  iron  wires;  tip  it  with 
sulphur,  and  proceed  as  in 
the  last  experiment. 

NOTE.  A  large  bottle  with  its 
bottom  removed,  and  resting  on 
a  dinner-plate  containing  water, 
makes  a  good  and  cheap  appara- 
tus for  the  last  three  experiments  ; 
and  it  will  also  answer  for  the 
next  experiment  if  no  globe  be  at 
hand. 

EXP.  16.  Place  a  bit  of  dry  phosphorus  as  large  as  a  pea  in 
a  deflagrating-spoon,  always  remembering  to  handle  the  phos- 
phorus with  pincers,  and  not  with  the  fingers ;  ignite  the 
phosphorus,  and  lower  it  into  a  globe  of  oxygen  gas.  Note 
the  color  of  the  flame.  This  experiment  produces  what  is 
known  as  the  "  Phosphorus  Sun." 

Ex.  All  these  experiments  furnish  examples  of  what  ?  Write  a  short 
description  of  each  experiment.  Why  do  these  phenomena  not  occur  in 
atmospheric  oxygen  ?  Enumerate  the  properties  of  oxygen. 

22.  Crystallization.  —  EXP.  17.  Place  the  residue  remain- 
ing in  the  oxygen  generator  (Exp.  15)  in  a  large  beaker-glass, 
and  add  about  a  litre  of  hot  distilled  water.  Agitate  the  con- 


16  OXYGEN. 

tents  of  the  beaker  with,  a  glass  rod  until  the  lumps  have  all 
disappeared;  the  potassium  chloride  is  now  dissolved,  while 
the  manganese  dioxide  is  unaltered.  Pour  the  contents  of  the 
beaker  on  a  large  filter-paper  fitted  to  an  appropriate  funnel, 
and  receive  the  filtrate  in  a  large  evaporating-dish.  Now 
evaporate  the  contents  of  the  dish  down  to  less  than  J1,  and 
then  set  the  dish  away  to  cool,  leaving  it  for  several  hours  un- 
disturbed. Crystals  of  potassium  chloride  will  form  in  the 
dish.  These  crystals  may  be  removed  from  the  solution  by 
filtering  through  a  fresh  filter-paper ;  and  they  may  be  dried 
by  simply  allowing  them  to  remain  on  the  filter-paper,  exposed 
to  the  air.  A  second  crop  of  crystals  may  be  had  by  concen- 
trating the  remaining  solution  ("mother  liquor"),  and  cooling 
as  before. 

NOTE.  The  manganese  dioxide  may  be  dried  on  the  filter-paper  and 
put  away  for  future  use. 

Ex.  What  processes  were  employed  in  obtaining  the  crystals  ?  Define 
crystallization  ;  "  mother  liquor  "  ;  a  crystal. 

23.  Ozone.  —  Oxygen  exists  in  a  peculiarly  modified  and 
unstable  form  called  ozone.  In  this  form  three  volumes 
of  ordinary  oxygen  are  condensed  to  two  volumes ;  accord- 
ingly the  formula  of  its  molecule  is  written  O3. 

Ozone  occurs  free  in  the  atmosphere  in  minute  quan- 
tities, probably  being  produced  through  the  agency  of 
electricity  and  by  the  vaporization  and  condensation  of 
atmospheric  moisture. 

EXP.  18.  Fill  a  test-tube  about  one-third  full  of  a  satu 
rated  solution  of  potassium  permanganate,  K2Mn208,  and  then 
cautiously  add  a  few  drops  of  sulphuric  acid,  H2S04.  Test 
the  escaping  gas  by  a  glowing  match.  Note  the  odor.  Sus- 
pend in  the  tube  a  strip  of  paper  moistened  in  a  solution  of 
starch  paste  and  potassium  iodide,  K. 

Ex.     Compare  ozone  with  pure  oxygen. 


OXYGEN.  17 

Ozone  is  much  more  energetic  in  its  action  than  the 
ordinary  oxygen,  and  especially  is  this  held  to  be  true 
concerning  its  action  upon  organic  matter  and  noxious 
exhalations  from  unhealthy  localities.  It  is  also  believed 
that  ozone  is  capable  of  destroying  many  kinds  of  disease 
germs. 

24.  Tests  for  Oxygen  and  Ozone.  —  1.  Free  oxygen  gas  is 
detected  by  its  lack  of  odor,  taken  together  with  its  action 
upon  a  glowing  match.  If  the  gas  be  dilute,  the  coal 
barely  continues  to  glow;  but  if  pure,  the  match  bursts 
into  flame. 

2.  Ozone  is  detected  by  its  odor,  by  its  kindling  a  glow- 
ing match,  and  by  its  coloring  blue  a  strip  of  paper  moist- 
ened in  a  solution  of  starch  paste  and  potassium  iodide. 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  The  molecular  weight  of  a  compound  substance  is  equal  to  the  sum 
of  the  atomic  weights  of  the  elements  forming  that  substance.     Compute 
the  molecular  weights  of  the  following :    HgO  ;   KC1O3  ;   KC1 ;   H2SO4  ; 
AgN03. 

2.  How  much  oxygen  is  there  in  100s  HgO  ? 

SUGGESTION.  The  molecular  weight  of  HgO  is  (Hg)  200  +  (O)  16  =  216. 
Now  ^T\  of  any  weight  of  HgO  is  oxygen. 

3.  How  many  litres  of  oxygen  at  0°  C.  and  760mm  are  there  in  484s  of 
oxygen  ?     See  data  for  computations. 

4.  How  many  litres  of  oxygen  at  0°  C.  and  IGQ™1*  may  be  had  from 
150s  KC103  ? 

5.  How  many  pounds  of  oxygen  are  there  above  one  square  foot  of  the 
earth's  surface  at  the  level  of  the  sea  ? 

SUG.  At  the  sea-level  the  atmosphere  weighs  about  fifteen  pounds  to 
the  square  inch. 

6.  Hold  a  short  piece  of  stick  phosphorus  by  means  of  a  pair  of  pin- 
cers, and  scrape  it  clean  under  water.     Loop  a  thread  around  the  phos- 
phorus, and  suspend  it  in  a  bottle  containing  a  few  drops  of  water.     Set 


18  OXYGEN. 

the  bottle  in  a  moderately  cool  place  (15°  to  20°  C.).  Now  suspend  in  the 
bottle  a  strip  of  paper  prepared  for  testing  ozone.  Note  from  time  to  time 
the  color  of  the  paper. 

7.  Set  a  Toepler-Holtz  machine  in  motion,  and  after  a  few  sparks  have 
passed,  note  the  odor.    Test  the  vicinity  of  the  poles  with  ozone  paper. 

8.  Explain  the  construction  of  the  Bunseii  burner.   Why  is  the  Bunsen 
flame  colorless  ? 

9.  Examine  the  blow-pipe  flame.    Note  the  inner  bluish  cone  and  the 
outer  slightly  luminous  layer.    This  latter  portion  of  the  flame  contains  an 
excess  of  oxygen,  heated  to  a  very  high  temperature.     Substances  placed 
in  this  part  of  the  flame  are  oxidized,  hence  the  name  Oxidizing  flame. 
The  best  place  to  hold  a  substance  to  be  oxidized  is  just  beyond  the 
bluish  tip. 

The  central  part  of  the  flame  contains  an  excess  of  highly  heated  carbon 
and  hydrogen,  and  substances  placed  within  the  cone  loose  their  oxygen 
or  are  reduced,  hence  the  name  Reducing  flame. 

10.  Bend  a  small  loop  on  a  piece  of  platinum  wire.    Heat  the  loop,  and 
dip  it  into  powdered  borax.     Fuse  the  borax  on  the  wire  to  a  colorless 
bead.     Now  slightly  moisten  the  bead  with  ferrous  sulphate,  FeSO4,  and 
heat  it  in  the  oxidizing  flame.     The  bead  becomes  reddish  in  color  when 
hot,  light  yellow  when  cold.     Again  heat  this  bead  in  the  reducing  flame  ; 
it  becomes  colorless.    Why  ? 


CHAPTER  H. 

HYDROGEN   AND   ITS   OXYGEN   COMPOUNDS. 

DATA  FOR  COMPUTATIONS.  —  Symbol,  H  ;  Molecular  Formula,  H2 ;  Atomic 
Weight,  1 ;  Specific  Gravity,  0.0692  ;  Weight  of  I1  at  0°  C.  and  760mm, 
0.0896«. 

25.  Occurrence.  —  Free  hydrogen  occurs  only  in  insignifi- 
cant quantities,  being  found  chiefly  in  volcanic  gases.     In 
its  compounds,  however,  hydrogen  occurs  plentifully.  Thus, 
of  water,  H2O,  it  constitutes  11.1  per  cent  by  weight ;  while 
it  is  always  present  in  ammonia,  acids,  and  organic  com- 
pounds. 

26.  Preparation  and  Properties.  —  Hydrogen  is  readily  ob- 
tained from  its  compounds,  such  as  water,  H2O,  and  from 
acids,  such  as  hydrochloric  acid,  HC1,  and  sulphuric  acid, 
H2SO4. 

EXP.  19.  Place  about  &  mercury  in  a  porcelain  mortar ; 
on  the  mercury  place  about  0.5g  metallic  sodium.  Now,  by 
means  of  a  pestle,  bear  the  sodium  down  through  the  mercury 
to  the  bottom  of  the  mortar,  and  then  twist  the  pestle  till  the 
sodium  and  mercury  unite  to  form  an  amalgam. 

Fill  a  test-tube  half  full  of  water,  and  into  this  drop  a  piece 
of  the  amalgam.  Xote  the  bubbles  of  gas  escaping,  and  note 
their  color  and  odor,  if  any.  Hold  the  tube  firmly,  and  care- 
fully bring  a  lighted  match  near  its  mouth. 

Ex.  What  became  of  the  mercury  used  in  making  the  amalgam? 
Kub  some  of  the  water  in  the  test-tube  between  the  thumb  and  finger, 
and  note  the  feeling.  Has  the  water  changed  ?  Dip  a  strip  of  red  litmus 

19 


20 


HYDROGEN  AND  ITS  OXYGEN  COMPOUNDS. 


paper  in  the  water,  and  note  the  change  in  the  color  of  the  paper.  Is  an 
alkali  present  ?  (Suo.  Alkalies  turn  red  litmus  paper  blue.)  Is  hydrogen 
inflammable  ?  Has  it  an  odor  or  a  color  ?  Define  an  amalgam. 

In  this  experiment  hydrogen  was  obtained  from  water. 
One  atom  of  sodium  displaced  or  set  free  one  atom  of 
hydrogen,  and  formed  the  alkali,  caustic  soda,  or  sodium 
hydroxide.  The  reaction  —  that  is,  the  changes  that  took 
place  —  can  best  be  shown  by  means  of  an 

EQUATION.  Thus,  Na  +  H20  =  NaOH  +  H.  This  equation  is  read, 
"Sodium  and  water  give  sodium  hydroxide  and  hydrogen."  Equations 
are  further  useful,  since  they  enable  us  to  tell  what  proportions,  by  weight, 
of  substances  take  part  in  chemical  reactions.  This  is  accomplished  by 
means  of  the  weights  of  the  atoms  and  of  the  molecules  represented  in 
the  equation.  For  example,  23  (Na)  +  18  (H20)  =  40  (NaOH)  +  1  (H). 
That  is,  23  parts,  by  weight,  of  sodium  react  with  18  parts  of  water  to 

give  40  parts  of  sodium  hydrox- 
ide and  1  part  of  hydrogen. 
Ex.  Explain  these  equations  : 
HgO  (heated)    =  Hg+0, 
and 

KC103  (heated)  =  KC1  +  3  O. 

EXP.  20.  Arrange  a  jar 
filled  with  water,  as  in  Fig. 
5.  Wrap  a  piece  of  sodium 
amalgam  in  wire  gauze,  and 
place  it  under  the  mouth  of  the  jar.  Hydrogen  rises  in  the 
jar.  Test  the  gas  by  raising  the  jar,  mouth  downwards,  and 
thrusting  a  lighted  taper  up  into  the  jar.  The  hydrogen 
will  burn  around  the  mouth  of  the  jar,  while  the  taper  will 
be  extinguished.  The  taper  may  be  relighted  in  the  burning 
gas.  A  slight  but  harmless  explosion  usually  terminates  the 
experiment. 

EXP.  21.  Half  fill  an  evaporating-dish  with  warm  water,  and 
then  drop  in  a  small  piece  of  pure  metallic  sodium  (Fig.  6). 
Also  try  in  this  way  a  small  piece  of  metallic  potassium. 


FIG. 


HYDROGEN  AND  ITS  OXYGEN  COMPOUNDS.     21 

NOTE.    This  experiment  may  terminate  with  a  slight  explosion. 

Ex.     What  advantage  is  gained  by  using  sodium  or  potassium  amal- 
gam ?     Is  the  water  in  the  evaporat- 
ing- dish    alkaline    after  adding  the 
metals  ?     Write  the  equation  for  the 
reaction  between  K  and 


EXP.  22.  Fit  a  cork  with  a 
straight-jet  delivery-tube  to  a 
generating-flask.  In  the  flask  .._-.-_-. 

place  (say)  10g  granulated  zinc. 
Now  fill  the  flask  one-third  full  of  dilute  sulphuric  acid,  made 
by  adding  one  part  of  acid  to  five  parts  of  water.  Place  the 
cork  and  jet  in  position,  and  when  the  air  is  expelled  from  the 
apparatus,  light  the  jet  of  escaping  gas.  Note  the  color  of 
the  flame.  Hold  a  piece  of  small  iron  wire  in  the  flame.  Ex- 
tinguish the  flame,  and  collect  the  gas  in  a  gas-bag. 

NOTE.  In  case  the  gas  is  not  given  off  freely,  add  to  the  contents  of 
the  flask  a  few  nails  or  a  few  small  crystals  of  copper  sulphate. 

In  this  experiment  the  hydrogen  is  obtained  from  sul- 
phuric acid  by  means  of  a  reaction  with  zinc,  thus,  — 

Zn  +  H2S04  =  ZnS04  +  H2. 

No  note  is  taken  of  the  water  added,  since  this  merely 
serves  to  dissolve  the  zinc  sulphate,  ZnSO4,  as  fast  as  that 
salt  is  formed. 

Ex.  What  is  the  color  of  the  hydrogen  flame  ?  Has  the  flame  a  high 
temperature  ?  By  means  of  a  rubber  tube  fit  a  common  clay  pipe  to  the 
gas-bag  filled  with  hydrogen,  and  blow  a  few  hydrogen  soap-bubbles.  Is 
hydrogen  lighter  than  air  ?  Touch  a  bubble  with  a  candle-  flame.  Write 
the  equation  for  Exercise  5  at  the  close  of  the  Introduction,  where  zinc 
and  hydrochloric  acid  react. 

EXP.  23.  Fire  the  hydrogen  pistol  to  illustrate  the  explo- 
siveness  of  a  mixture  of  hydrogen  and  oxygen. 

EXP.  24.  Fill  a  collodion  balloon  with  hydrogen  gas,  and 
then  release  the  balloon  in  the  laboratory.  After  some  hours 


22 


HYDROGEN  AND  ITS  OXYGEN  COMPOUNDS. 


the  balloon  will  settle  to  the  floor.     When  this  has  occurred, 
test  the  gas  in  the  balloon  for  hydrogen. 

Some  or  all  of  the  hydrogen  in  the  balloon  has  passed 
out  into  the  air  through  the  pores  of  the  balloon,  and  air 
has  entered  through  the  same  channels.  This  illustrates 
what  is  termed  Diffusion  of  gases  through  porous  parti- 
tions. It  is  in  this  way  that  oxygen  passes  through  the 
delicate  membranes  of  the  pulmonary  capillaries  to  purify 
the  blood  in  its  passage  through  the  lungs. 


FIG.  7. 

EXP.  25.  Arrange  a  delivery-tube  for  a  hydrogen  appa- 
ratus, as  shown  in  Fig.  7.  Using  the  same  materials  as  in 
Exp.  22,  fill  a  jar  with  hydrogen.  Then  carefully  lift  up 
the  jar,  keeping  its  mouth  downwards.  Now  slowly  bring 
the  mouth  of  the  jar  upward,  underneath  the  mouth  of  a 
second  jar,  held  mouth  downward.  When  the  first  jar  has 
reached  an  upright  position,  remove  it,  and  test  its  contents 
for  hydrogen.  Also  test  the  contents  of  the  second  jar  for  the 
same  gas. 

Ex.    What  has  occurred  ?    Enumerate  the  properties  of  hydrogen. 

27.  Test  for  Hydrogen.  —  Hydrogen  may  be  detected  by 
its  flame  and  by  its  behavior,  as  in  the  preceding  experi- 
ments. 


COMPOUNDS  OF  HYDROGEN  WITH  OXYGEN. 


23 


COMPOUNDS   OP   HYDROGEN   WITH   OXYGEN. 

28.  Hydrogen  and  oxygen  unite  to  form  but  two  chem- 
ical compounds :  water,  H2O ;  and  hydrogen  dioxide,  H2O2. 
Of  these  compounds,  water  is  by  far  the  most  important. 

WATER. 

29.  Occurrence.  —  Water  occurs   widely   distributed  in 
nature.     Permeating  the  atmosphere  and  soil,  flowing  in 
streams  and  forming  lakes  and  oceans,  water  is  everywhere 
found.     Although  the  properties  of  water  are  familiar  to 
all,  nevertheless,  since  this  is  the  first  chemical  compound 
to  be  studied  in  detail,  it  will  be  necessary  to  make  a  few 
experiments  illustrating  some  of  the  methods  employed  by 
chemists  in  investigating  the  composition  and  properties 
of  bodies. 

30.  Preparation  and  Prop- 
erties. —  Let  us  first  make 
a  qualitative  experiment  in 
order  to  learn  if  water  can 
be  produced  synthetically. 

EXP.  26.  Arrange  an  ap- 
paratus as  shown  in  Fig.  8. 
G  is  a  hydrogen  generator, 
containing  zinc  and  dilute 
sulphuric  acid.  B  is  a  dry- 
ing-bulb, containing  granu- 
lated calcium  chloride,  CaCL.  Introduce  the  acid  through 
the  funnel-tube,  and  when  the  apparatus  is  free  from  air, 
ignite  the  hydrogen  gas  escaping  through  the  jet,  and  place 
the  bell-jar,  E,  over  the  flame.  Note  what  collects  on  the 
sides  of  the  jar. 


FIG.  8. 


24 


COMPOUNDS  OF  HYDROGEN  WITH  OXYGEN. 


Ex.  Why,  in  this  experiment,  should  the  hydrogen  gas  be  perfectly 
dry  ?  When  the  hydrogen  is  burning,  with  what  constituent  of  the  air 
does  it  unite  ?  What  substances,  then,  enter  into  the  composition  of 
water? 

Next  let  us  make  a  quantitative  experiment  to  determine 
synthetically  in  what  proportions,  by  volume,  hydrogen 
and  oxygen  unite  to  form  water.  This  may  be  accom- 
plished by  means  of  the  apparatus  (lire's  eudiometer) 
shown  in  Fig.  9. 

EXP.  27.  The  graduated  limb  and  a  part 
of  the  plain  limb  are  to  be  filled  with  mer- 
cury. Then,  by  means  of  a  curved  glass  tube, 
10  divisions  of  the  graduated  limb  are  filled 
with  pure  oxygen;  25  divisions  of  pure  hy- 
drogen are  next  to  be  added.  Now  bring  the 

mercury  to  the  same  level 

in  both  limbs,  and  while 

firmly  holding  the  thumb 

over  the  plain  limb,  pass 

an  electric  spark  through 

the  wires  attached  to  the 

graduated    limb.      20    di- 
visions of  hydrogen  will  p 

unite  with  10  divisions  of 

oxygen  to  form  water.    It 
thus  appears  that  these  gases  unite  in  the  proportion  of  2 
volumes  of  hydrogen  to  1  volume  of  oxygen. 

These  two  experiments  illustrate  how  the  composition 
of  certain  bodies  may  be  determined  by  Synthesis.  An- 
other and  more  extensively  employed  method  is  termed 
Analysis.  In  the  case  of  water,  the  analysis  may  be  made 
by  a  process  termed  Electrolysis.  The  apparatus  (Hoff- 
mann's apparatus)  used  is  shown  in  Fig.  10. 


FIG.  9. 


FIG.  10. 


COMPOUNDS    OF    HYDROGEN    WITH   OXYGEN.  25 

EXP.  28.  Add  one  part,  by  weight,  of  sulphuric  acid  to  20 
parts  of  distilled  water.  Open  the  stop-cocks  S  and  S',  and 
then  pour  the  acidulated  water  into  the  tube  B  until  it  issues 
from  the  tubes  0  and  H.  Close  the  stop-cocks,  and  fill  B  up 
to  the  bulb.  Connect  the  platinum  wire  Z,  which  is  melted 
through  the  tube  H  and  terminates  in  a  platinum  strip,  with 
the  zinc  pole  of  a  Grove's  battery,  consisting  of  five  or  six 
cells.  Also  connect  the  platinum  wire  P  (which  is  like  Z  in 
every  respect)  to  the  platinum  pole  of  the  battery.  Hydrogen 
collects  in  the  tube  H,  and  oxygen  in  the  tube  0.  Note  the 
comparative  volumes  of  the  gases  collected. 

The  hydrogen  may  be  tested  by  slightly  opening  the  stop- 
cock S'  and  igniting  the  escaping  gas.  Open  the  stop-cock  S, 
and  test  the  oxygen  by  means  of  a  glowing  match. 

Ex.  What  relative  volumes  of  hydrogen  and  oxygen  were  liberated  ? 
Compare  the  results  of  this  experiment  with  those  obtained  in  Exp.  27. 
Define  synthesis ;  analysis ;  a  qualitative  experiment ;  a  quantitative 
experiment ;  qualitative  analysis  ;  quantitative  analysis  ;  electrolysis  ; 
an  electrolyte. 

The  proportions,  by  weight,  in  which  oxygen  and  hydro- 
gen unite  to  form  water  may  now  be  determined. 

The  preceding  experiments  show  conclusively  that  in 
water  2  volumes  of  hydrogen  are  united  with  1  volume  of 
oxygen.  Now  let  us  assign  some  absolute  value  to  each 
volume,  so  that  the  weights  of  the  volumes  may  be  deter- 
mined. For  example :  take  21  of  hydrogen  and  I1  of  oxy- 
gen ;  then,  multiplying  the  number  of  litres  of  each  gas 
by  the  weight  of  I1  of  that  gas,  the  proportion,  by  weight, 
becomes  2  x  0.0896  : 1  x  1.430  or  0.1792  : 1.430.  This  ratio 
reduced  to  its  lowest  terms  becomes  very  nearly  1:8;  i.e.  1 
part,  by  weight,  of  hydrogen  unites  with  8  parts,  by  weight, 
of  oxygen. 

One  way  of  determining  the  molecular  formula  of  water 
is  as  follows :  — 


26      COMPOUNDS  OF  HYDROGEN  WITH  OXYGEN. 

It  must  be  remembered  that  the  symbols  of  the  elements 
represent  both  atoms  and  the  weights  of  the  atoms.  Now, 
since  the  atomic  weight  of  oxygen  is  16,  the  ratio  of  1 :  8 
would  only  require  \  an  atom  of  oxygen  to  1  atom  of 
hydrogen,  which  is  not  supposable;  but  if  we  multiply 
the  ratio  by  2,  it  becomes  2  : 16,  or  2  atoms  of  hydrogen 
to  1  of  oxygen.  Now  these  are  the  fewest  number  of 
atoms  that  could  possibly  form  water.  Moreover,  experi- 
ment has  shown  that  the  molecular  weight  of  water  is  18. 
Hence  there  is  but  one  conclusion:  no  larger  number  of 
9,toms  enter  into  the  molecule,  and  water  is  H2O.  How 
molecular  weights  are  determined  will  be  explained  here- 
after. 

The  solvent  action  of  water  upon  many  substances  is  well 
understood.  Sugar,  salt,  and  similar  substances,  as  well  as 
many  liquids  and  gases,  are  readily  soluble  in  water.  But 
the  solvent  powers  of  water  are  greater  than  superficial 
observation  would  indicate. 

EXP.  29.  Place  a  few  clean  pine  shavings  in  an  evaporat- 
ing-dish  half  full  of  ordinary  well  water.  Boil  the  contents 
of  the  dish  for  a  short  time,  and  then  filter.  Note  the  taste 
and  odor  of  the  filtrate 

Ex.  Has  the  water  dissolved  a  portion  of  the  pine  ?  What  makes 
water  that  has  stood  in  wooden  pails  "  taste  "  ? 

Limestone,  or  calcium  carbonate,  CaCO3,  and  ferrous 
carbonate,  FeCO3,  are  insoluble  in  pure  water ;  but  in 
water  charged  with  carbonic  acid  gas,  CO2,  these  sub- 
stances are  readily  soluble.  When  the  carbonic  acid  is 
expelled  by  boiling,  they  both  become  insoluble  again  and 
are  precipitated.  In  the  case  of  many  other  substances, 
such  as  certain  organic  compounds,  and  metals  like  lead 
and  copper,  impure  water  will  act  as  a  solvent  where  pure 
water  would  have  no  action. 


COMPOUNDS   OF   HYDROGEN   WITH   OXYGEN.  27 

EXP.  30.  Fill  a  beaker  with  ordinary  well-water.  Place 
the  beaker  on  the  sand-bath,  and  boil  the  water  for  a  short 
time.  Note  any  cloudiness  or  precipitate  that  may  appear  in 
the  water. 

Ex.  Why  did  the  precipitate  form  ?  Why  is  a  crust  formed  on  the 
inside  of  a  tea-kettle  in  which  hard  water  is  boiled  ?  Explain  the  forma- 
tion of  fossils.  Knowing  that  the  coloring-matter  of  vegetation  is  partly 
composed  of  iron,  explain  why  the  waters  of  springs  and  creeks  deriving 
their  supplies  from  marshy  lands  contain  iron.  Why  do  these  waters 
deposit  iron  ores  ?  Explain  the  formation  of  sedimentary  rocks.  How 
did  the  deposition  of  sandstone  differ  from  that  of  limestone  ?  Which 
will  dissolve  more  common  salt,  hot  or  cold  water  ?  Why  is  water  flow- 
ing through  lead  pipes  dangerous  to  drink  ?  Why  is  drinking-water  liable 
to  contain  organic  matter  ?  In  what  ways  is  water  useful  to  plants  and 
animals  ? 

Besides  acting  as  a  solvent,  water  fulfils  another  ex- 
tremely important  office  :  it  acts  as  a  heat  regulator.  In 
changing  lkg  of  ice  from  a  solid  at  0°  C.  to  a  liquid  at 
the  same  temperature,  79  heat-units,  or  calories,  are  ren- 
dered latent;  while  into  lkg  of  water,  in  passing  from  a 
liquid  at  100°  C.  to  steam  at  100°,  536  calories  disap- 
pear. When  water  freezes,  or  when  steam  condenses, 
the  latent  heat  is  again  given  up  to  the  atmosphere  or  -to 
surrounding  objects.  Moreover,  water  receives  and  parts- 
with  its  heat  very  slowly,  and  thus  it  modifies  climatic 
extremes. 

Water  is  at  its  maximum  density  at  +  4°  C.  When  its 
temperature  passes  either  above  or  below  this  point,  water 
expands.  Consequently,  ice  is  lighter  than  water;  and 
forming,  as  it  does,  at  the  surface  of  lakes  and  rivers,  it 
acts  as  a  protection  to  the  water  underneath.  Snow  serves 
as  a  protection  to  the  ground,  and  clouds  prevent  a  rapid 
loss  of  heat  by  radiation  from  the  surface  of  the  earth. 


28 


COMPOUNDS   OF   HYDROGEN   WITH   OXYGEN. 


FIG. 


EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  How  many  litres  at  0°  C.  and  760mm  are  there  in  4.326s  hydrogen  ? 

2.  How  many  litres  of  oxygen  would  be  required  to  form  water  with 

the  hydrogen  in  the  preceding  exer- 
cise ?  What  would  the  oxygen  weigh  ? 
How  much  water  would  be  formed  ? 

3.  Bearing  in  mind  that  one  calorie 
of  heat  will  raise  lks  of  water  through 
1°  C.,  how  many  calories  would  be 
required  to  convert  10kB  of  ice  at  0° 
into  steam  at  100°  ? 

4.  Name   10  substances  that  are 
soluble  in  water,  and   10  that  are 
insoluble. 

5.  Prepare  and  test  hydrogen  di- 
oxide, H202,  thus  :  Make  a  mixture 
of  2CC  sulphuric  acid  and  20CC  water. 
Place  the  mixture  in  a  beaker,  and 
when  cool,  add,  with  constant  stir- 
ring, 6s  finely  pulverized  barium  dioxide,  Ba02.    Filter  the  contents  of  the 
beaker,  or  allow  the  white  precipitate  to  subside,  thus  obtaining  a  clear 
solution  of  hydrogen  dioxide  :  BaO2  +  H^SO^  =  H2O2  +  BaSO4.     The  white 
precipitate  is  barium  sulphate. 

Test  the  hydrogen  dioxide  thus: 
To  about  a  half  of  a  test-tube  of 
the  solution  add  successively  2  or 
3  drops  of  sulphuric  acid,  5  or  6 
drops  of  potassium  dichromate, 
K2Cr2O7,  and  about  2CC  ether,  FIG.  12. 

(C2H5)2O.     Now  shake  the  tube 
thoroughly,  and  note  the  blue-colored  solution  obtained. 

6.  Determine  the  total  residue  in  a  sample  of  drinking-water,  thus : 
Weigh  an  evaporating-dish,  and  in  it  carefully  evaporate  to  dryness  over 
a  water-bath  one-half  litre  of  the  sample.    Place  the  dish  and  its  contents 
over  a  dish  containing  strong  sulphuric  acid,  and  cover  the  whole  with  a 
small  bell-jar.    When  cool,  weigh  the  dish  and  its  contents  ;  from  this 
weight  subtract  that  of  the  dish,  and  multiply  the  difference  by  2.    The 
result  is  the  total  residue  per  litre  sought. 

7.  Explain  the  principles  involved  in  the  oxyhydrogen  blow-pipe  (Fig. 
11).    The  tip  is  shown  in  Fig.  12. 


CHAPTER  III. 


NITROGEN    AND    ITS     COMPOUNDS   WITH     HYDROGEN 
AND    OXYGEN. 

DATA  FOR  COMPUTATIONS.  —  Symbol,  N  ;  Molecular  Formula,  N2 ;  Atomic 
Weight,  14 ;  Specific  Gravity,  0.971 ;  Weight  of  I1  at  0°  C.  and  TeO11"11, 
1.256*. 

31.  Occurrence.  —  Nitrogen  is  found  free  in  the  atmos- 
phere, of  which  it  constitutes  nearly  four-fifths  part  by 
volume,  or  77  per  cent  by  weight.     In  compounds,  nitro- 
gen occurs  in  such  substances  as  ammonia,  NH3 ;  potassium 
nitrate,  or  saltpeter,  KNO3;  sodium  nitrate,  or  Chili  salt- 
peter, NaNO3 ;  and  in  many  organic  compounds. 

32.  Preparation  and  Proper- 
ties. —  EXP.  31.     Float  an  iron 
sand-bath  or  a  tin  cup  on  the 
water  of  the  pneumatic  trough, 
or   of    any   convenient    vessel. 
Into  the   cup   drop    a    bit    of     ^ 
phosphorus.     Ignite  the  phos-  jB 
phorus,     and     then     carefully    ! 
place  down  over  it  a  bell-jar 
(Fig.    13).     White   fumes    of 
phosphorus     pentoxide,     P2O5, 

and  perhaps  of  the  trioxide,  P203,  quickly  fill  the  jar.  These 
fumes  soon  subside,  and  dissolve  in  the  water,  leaving  the 
nitrogen  nearly  pure. 

Ex.  What  substance  was  removed  from  the  air  in  the  jar  by  the 
burning  phosphorus  ?  Are  the  fumes  formed  solid  or  gaseous  ?  Why 
would  gaseous  products  in  this  experiment  be  objectionable  ? 

29 


FIG.  13. 


30  NITROGEN    AND   ITS    COMPOUNDS. 

EXP.  32.  Lower  a  burning  taper  into  a  jar  of  nitrogen. 
Try  a  glowing  match.  Compare  the  phenomena  observed  with 
those  obtained  in  oxygen. 

EXP.  33.     Place  a  live  mouse  in  a  jar  of  nitrogen. 

Ex.  Is  nitrogen  a  supporter  of  combustion  ?  of  life  ?  What  purpose 
does  nitrogen  serve  in  the  atmosphere  ?  Is  nitrogen  poisonous  ?  Would 
a  mixture  of  air  and  nitrogen  explode  ?  Has  nitrogen  any  color  or  odor  ? 
Enumerate  the  properties  of  nitrogen. 

Nitrogen  possesses  a  very  feeble  chemism  for  the  other 
elements,  in  consequence  of  which  it  does  riot  enter  directly 
into  combination  with  them.  Indirectly,  however,  it  forms 
many  important  compounds,  as  will  appear  further  on. 
Owing  to  its  passive  nature,  nitrogen  in  small  quantities 
is  not  easily  detected. 

AMMONIA,  NH3. 

33.  Occurrence.  —  Ammonia,  which  is  a  chemical  com- 
pound of  nitrogen  and  hydrogen,  is  a  very  important  sub- 
stance. It  occurs  widely  distributed  in  the  atmosphere 
and  in  nearly  all  waters.  Rain,  snow,  ice,  and  the  waters 
of  springs,  deep  and  shallow  wells,  lakes,  streams,  and 
seas,  all  contain  considerable  quantities  of  ammonia. 

It  is  a  wise  provision  that  ammonia  is  thus  distributed, 
since  from  it  plants  build  up  the  nitrogen-bearing  portions 
of  their  tissues,  —  the  albuminoids,  —  found  in  seeds,  roots, 
and  leaves.  Animals,  in  turn,  consume  these  tissues,  and 
thus  acquire  the  material  for  building  up  the  nitrogen- 
bearing  portions  of  their  bodies,  —  the  proteids,  —  found 
in  muscles  and  in  other  parts  of  the  body. 

Ammonia  compounds  occur  but  sparingly  in  nature, 
although  they  are  important  manufactured  articles  of  com- 
merce. 


NITROGEN   AND   ITS   COMPOUNDS.  31 

34.  Preparation  and  Properties.  —  EXP.  34.  In  one  hand 
place  a  little  powdered  quicklime,  CaO,  and  in  the  other  put 
an  equal  bulk  of  powdered  ammonium  chloride,  or  sal-am- 
moniac, NH4C1.  Note  that  neither  has  an  odor.  Rub  these 
substances  between  the  palms  of  the  hands,  and  carefully 
smell  the  gas  produced  :  — 

CaO  +  2  NH4C1  =  2  NH3  +  CaCl2  +  H20. 
The  residue  in  the  hands  is  chiefly  calcium  chloride, 


Ex.  Has  ammonia  a  color  ?  Place  a  strip  of  moistened  red  litmus 
paper  in  the  fumes,  and  note  whether  they  are  alkaline. 

In  this  experiment,  ammonia  was  liberated  from  one  of 
its  compounds  by  means  of  a  stronger,  or  "fixed"  alkali. 
Since  ammonia  and  its  compounds  are  vaporized  by  the 
action  of  heat,  it  is  called  the  "  volatile  "  alkali  ;  while  all 
other  alkalies  are  not  readily  vaporized,  and  are  designated 
as  the  "  fixed  "  alkalies.  All  the  fixed  alkalies  will  liberate 
ammonia  from  its  compounds. 

EXP.  35.  To  a  solution  of  any  ammonium  salt  in  a  test- 
tube  add  a  solution  of  potassium  hydroxide,  KOH.  Warm 
the  tube  gently,  and  test  as  usual  the  properties  of  the  gas 
evolved.  Test  the  alkalinity  of  the  gas  by  means  of  a  moist 
red  litmus  paper. 

Ammonia  gas  dissolved  in  water  is  sold  in  every  drug 
store  as  aqua  ammonice.  Aqua  ammonise  is  prepared  from 
about  the  same  materials  used  in  Exp.  34.  The  ammonium 
chloride  or  sulphate  is  procured  from  gas-works,  where  it 
is  obtained  as  a  by-product  by  passing  the  crude  gas  from 
the  retorts  through  dilute  hydrochloric  or  sulphuric  acid. 

The  interesting  process  of  manufacturing  aqua  ammonise 
is  illustrated  in  Exp.  36,  which  also  shows  a  general  pro- 
cess of  dissolving  gases  in  water.  Sometimes  the  gas  is 
forced  iuto  the  water  by  means  of  its  own  pressure,  ol> 


32 


NITROGEN   AND   ITS   COMPOUNDS. 


tained  by  closing   air-tight  the   generator,  the  washing- 
apparatus,  and  the  receiver. 

EXP.  36.  Arrange  an  apparatus  as  in  Fig.  14.  Then  take 
(say)  50g  powdered  quicklime  and  100g  ammonium  chloride, 
and  moisten  each  separately  with  water  until  thick  pastes  are 
formed.  Disconnect  F,  and  rapidly  introduce  these  pastes  into 
it,  and  join  immediately  with  the  wash-bottle  A,  which  acts  as 


FIG.  14. 

a  safety  apparatus  to  prevent  any  water  from  flowing  back  into 
the  generating-flask  F.  B  and  C  are  here  used  as  condensers, 
and  the  ammonia  in  passing  through  them  is  dissolved  in  the 
water  they  contain.  It  is  best  to  surround  B  and  C  with 
pounded  ice  and  salt.  Aqua  ammonise  is  found  in  these  two 
bottles  at  the  conclusion  of  the  experiment. 

Ammonia  is  very  soluble  in  water.  lcc  of  water,  at  0°  C., 
dissolves  1148CC  of  ammonia. 

Atmospheric  ammonia  is  produced  by  the  decay  of  nitrog- 
enous organic  matter ;  and  through  the  agency  of  atmos- 
pheric moisture  it  finds  its  way  into  the  waters  of  all 
localities. 

Ammonia  was   formerly  prepared   by  distilling   hoofs, 


NITROGEN   AND  ITS   COMPOUNDS.  33 

hides,  and  horns,  whence  arose  the  name  of  "spirits  of 
hartshorn." 

EXP.  37.  Place  a  few  drops  of  ammonia  on  a  piece  of  por- 
celain or  platinum  foil,  and  carefully  evaporate  to  dry  ness. 
Next  treat  in  a  similar  manner  a  few  drops  of  hydrochloric 
acid,  HC1.  Does  either  give  a  residue  ?  Now  make  a  mixture 
of  the  two,  and  proceed  as  before.  Note  the  residue. 

Ammonia  unites  with  acids  to  form  salts,  as  shown  in 
the  foregoing  experiment :  — 


The  salt  is  called  ammonium  chloride,  and  the  group  of 
atoms,  NH4,  is  called  Ammonium,  owing  to  some  resem- 
blances which  it  bears  to  the  metals. 

Under  a  pressure  of  seven  atmospheres,  at  15.5°  C.,  am- 
monia condenses  to  a  liquid.  When  this  liquid  vaporizes, 
as  in  the  case  of  water,  large  quantities  of  heat  are  rendered 
latent.  Advantage  has  been  taken  of  this  to  manufacture 
ice.  Liquid  ammonia  is  simply  allowed  to  evaporate  in 
closed  iron  pipes  over  which  water  is  slowly  trickling. 

Since  ammonia  neutralizes  acids,  it  may  be  applied  when 
acids  are  spilled  on  the  clothes  or  on  the  flesh.  Again, 
when  poisonous  or  irritating  gases  have  been  inhaled, 
ammonia  vapors  act  as  an  antidote.  When  ammonia  is 
inhaled,  it  produces  a  stimulating  effect  upon  the  system. 

35.  Tests  for  Ammonia.  —  To  a  solution  supposed  to  con- 
tain ammonia  add  a  solution  of  potassium  hydroxide,  KOH, 
and  warm  gently.  If  ammonia  be  present,  it  may  be  recog- 
nized— 

(1)  By  its  odor. 

(2)  By  its  turning  moistened  red  litmus  paper  blue. 
By  holding  a  warm  glass  rod,  which  has  been  mois- 


34  NITROGEN   AND   OXYGEN. 

tened  in  hydrochloric  acid,  over  the  tube,  white  fumes  of 
ammonium  chloride,  NH4C1,  may  be  seen,  and  the  rod 
when  dry  will  be  found  coated  with  the  same  salt. 


NITROGEN    AND    OXYGEN. 

36.    There  are  five  compounds  of  nitrogen  and  oxygen 

known :  — 

Nitrogen  monoxide,  N20. 
Nitrogen  dioxide,  N202,  or  NO. 
Nitrogen  trioxide,  N203. 
Nitrogen  tetroxide,  N204,  or  NO2. 
Nitrogen  pentoxide,  N205. 

Of  these  compounds,  the  first  is  of  most  practical  im- 
portance. All  are  gases  except  the  last,  which  is  a  crys- 
talline solid.  The  last  four  will  receive  but  a  passing 
notice. 

The  second  oxide  is  formed  when  a  metal  and  nitric  acid, 
HNO3,  react.  When  the  gas  thus  produced  escapes  into 
the  air,  it  absorbs  oxygen,  producing  varying  amounts  of 
the  next  two  higher  oxides,  and  thus  giving  rise  to  the 
brownish  red  fumes  always  noticed  when  nitric  acid  is 
acting  on  metals,  thus :  — 

EXP.  38.  Place  a  bit  of  copper  in  an  evaporating-dish,  and 
add  enough  nitric  acid  to  cover  the  copper.  Warm  the  dish 
gently,  and  note  the  colored  fumes  above  the  dish :  — 

3  Cu  +  8  HN03  =  3  Cu(N03)2  +  2  NO  +  4  H20. 

Portions  of  the  nitrogen  dioxide  unite  with  the  oxygen  of  the 
air  thus :  — 

NO-f  0  =  N02  and  2NO  +  0  =  N203. 

The  blue  salt  formed  is  copper  nitrate,  Cu(N03)2. 


NITROGEN   AND   OXYGEN.  35 

NITROGEN  MONOXIDE,  N2O. 

37.  Preparation  and  Properties.  —  This  gas  is  known  as 
nitrous  oxide,  and  also  as  "  laughing-gas."  It  never  occurs 
free,  but  it  is  manufactured  by  dentists  and  by  others  for 
anaesthetic  purposes.  There  are  several  methods  of  obtain- 
ing nitrogen  monoxide,  but  the  one  always  used  consists 
in  decomposing  ammonium  nitrate,  NH4NO3,  by  means  of 

heat :  -  NH4N03  (heated)  =  N20  +  2  H2O. 

EXP.  39.  Place  in  a  test-tube  a  small  quantity  of  ammonium 
nitrate,  and  heat  it  carefully  in  the  Bunsen  flame.  Note  the 
odor  of  the  gas  produced,  and  test  it  with  a  glowing  match 
and  then  with  a  blazing  match.  Compare  the  results  with  those 
obtained  in  oxygen. 

For  generating  large  quantities  of  nitrous  oxide,  com- 
mercial ammonium  nitrate  is  often  employed.  Coming 
from  this  source,  the  gas  is  apt  to  contain  impurities  dan- 
gerous to  inhale,  such  as  nitrogen  dioxide,  NO,  and  per- 
haps some  chlorine  or  chlorine  compounds.  In  order  to 
remove  these  impurities,  the  gas  is  washed,  as  shown  in 
the  following  experiment,  which  also  illustrates  the  usual 
method  of  washing  gases  :  — 

EXP.  40.  Arrange  an  apparatus  as  shown  in  Fig.  15.  The 
generator  is  fitted  with  a  bent,  one-bulb,  thistle-top  tube,  con- 
taining a  small  quantity  of  mercury.  This  makes  a  safety- 
valve.  The  first  wash-bottle  contains  a  warm  solution  of  fer- 
rous sulphate,  FeSO^  to  remove  any  nitrogen  dioxide.  The 
second  bottle  contains  a  warm  solution  of  potassium  hydrox- 
ide, KOH,  to  remove  any  chlorine.  The  third  bottle  contains 
warm  water.  Use  about  50g  of  ammonium  nitrate  in  the  gen- 
erator, and  employ  a  moderate  heat.  Collect  the  gas  in  gas- 
bags, as  it  is  soluble  in  water,  and  more  especially  in  cold  than 


36  NITROGEN   AND    OXYGEN. 

in  warm  water.     Inhale  some  of  the  gas  thus  prepared,  and 
note  the  odor  and  the  sweetish  taste. 

When  inhaled  in  considerable  quantities,  nitrogen  mon- 
oxide produces  its  effects  upon  the  system  in  the  following 
order :  intoxication,  and  singing  in  the  ears ;  insensibility  ; 
and  finally,  if  the  inhalation  be  continued  long  enough, 
death. 


FeSO4  KOH 

FIG.  15. 

At  0°  C.,  30  atmospheres'  pressure  condenses  this  gas  to 
a  liquid ;  and  if  this  liquid  be  mixed  with  carbon  bisul- 
phide, CS2,  and  evaporated  in  vacuo^  the  very  low  temper- 
ature of  — 140°  C.  is  produced. 

38,  Tests  for  Nitrogen  Monoxide,  —  This  gas  closely  re- 
sembles oxygen,  from  which  it  is  easily  distinguished  by 
its  sweetish  taste  and  odor,  and  by  its  solubility  in  cold 
water. 

39.  The  Law  of  Multiple  Proportions,  —  By  inspecting  the 
formulae  of  the  oxides  of  nitrogen,  it  will  be  seen  that  the 


quantities  of  oxygen  that  are  umtedwlQk  'IH  "KTllo  one 
another  as  1:2:3:4:5,  while  the  nitrogen  remains  con- 
stant. 

Such  relations  as  these  are  frequently  found  in  the  com- 
pounds of  elements.  In  every  case  the  ratio  is  a  simple 
one,  and  the  element  that  increases  does  so  by  whole  num- 
bers, and  not  by  fractions.  This  is  in  strict  conformity 
with  the  atomic  theory.  The  law  of  multiple  proportions 
may  be  stated  thus  :  — 

If  two  elements,  A  and  B,  form  several  compounds  with 
each  other,  and  if  we  take  any  fixed  amount  of  A,  then  the 
different  quantities  of  B  which  combine  with  this  fixed  amount 
of  A  bear  a  simple  ratio  to  one  another. 

40.  Determination  of  Molecular  Weights.  —  The  molecule 
of  any  substance  has  been  defined  as  the  smallest  particle 
of  that  substance  which  can  exist  in  a  free  state.  If  now 
we  take  a  molecule  of  a  gas  like  hydrochloric  acid,  HC1, 
that  molecule  must  have  at  least  one  atom  each  of  hydro- 
gen and  chlorine,  and  its  molecular  weight  will  be  the 
sum  of  the  weights  of  these  two  atoms.  Thus,  for  hydro- 
chloric acid  we  have  1  +  35.5  =  36.5.  Therefore  in  such 
simple  gases,  where  the  atomic  weights  are  known,  the 
problem  presents  no  difficulties.  But  when  the  constitu- 
tion of  a  gas  is  more  complex,  as  in  the  second  and  fourth 
oxides  of  nitrogen,  difficulties  arise.  But  it  has  been 
found  that  when  the  molecular  weight  of  a  gas  is  divided 
by  its  specific  gravity,  a  nearly  constant  quantity  is  ob- 
tained, i.e.  about  28.88.  Hence  it  follows  that  in  any 
gas  the  molecular  weight  =  the  specific  gravity  X  28.88. 
In  such  cases,  then,  the  specific  gravity  of  the  gas  gives 
a  key  to  the  molecular  weight.  Thus,  in  the  second 


38  THE   NITKOGEN    OXACIDS. 

oxide  of  nitrogen,  the  specific  gravity  found  is  1.03845. 
Now  1.03845  x  28.88  =  29.99,  or  practically  30.  This 
would  make  the  molecular  formula  NO,  and  not  N2O2. 
In  the  same  way  the  molecular  weight  of  the  fourth 
oxide  of  nitrogen  was  found  to  be  about  46,  and  its 
formula  NO2.  There  is  no  certain  method  of  determin- 
ing the  molecular  weights  of  substances  which  cannot  be 
vaporized. 

41.  Avogadro's  Hypothesis,  —  Avogadro  explained  the  re- 
lation existing  between  the  molecular  weight  and  the  spe- 
cific gravity  of  a  gas  by  the  following  hypothesis  :  Under 
the  same  conditions  of  temperature  and  pressure,  equal  vol- 
umes of  all  gases  contain  the  same  number  of  molecules. 
Thus  if  one  cubic  centimetre  of  one  gas  has  (say)  1000 
molecules,  then  a  cubic  centimetre  of  any  other  gas  under 
the  same  conditions  will  also  have  1000  molecules.  This 
hypothesis  has  been  of  the  greatest  importance  to  a  cor- 
rect conception  of  some  facts  in  theoretical  chemistry.  See 
pp.  41  and  42. 


THE    COMPOUNDS    OF    NITROGEN,    OXYGEN,    AND 
HYDROGEN;     OR,    THE    NITROGEN    OXACIDS. 

42.  These  three  elements  unite  to  form  three  com- 
pounds, called  acids :  — 

Hyponitrous  acid  (hypothetical),  HNO. 
Nitrous  acid,  HN02. 

Nitric  acid,  HN03. 

Only  the  last  two  acids  have  been  isolated,  and  none  of 
them  occur  free  in  nature  in  any  considerable  quantity. 
Nitric  acid  is  the  most  important  acid  of  this  series, 


THE   NITROGEN   OXACIDS.  39 

Nitrous  acid  may  be  prepared  by  dissolving  nitrogen 
trioxide  in  water  :  — 


This  acid  is  unimportant,  but  its  salts  —  the  nitrites  — 
occur  in  impure  well-water,  being  produced  during  the 
decay  and  nitrification  of  organic  nitrogenous  substances. 

NITRIC  Aero,  HNO3. 

43.  Occurrence.  —  The  compounds  of  nitric  acid,  potas- 
sium  nitrate,  KNO3,   and  sodium   nitrate,  NaNO3,  occur 
quite  plentifully  in  nature,  and  it  is  from  these  substances 
that  this  very  important  acid  is  obtained. 

44.  Preparation  and  Properties.  —  EXP.  41.     Place  a  small 
quantity  of  powdered  potassium  nitrate,  KN03,  in  a  test-tube, 
and  then  add  a  few  drops  of  sulphuric  acid.     Warm  the  con- 
tents of  the  tube  gently,  and  note  the  fumes  given  off.     Test 
the  fumes  with  moist  blue  litmus  paper. 

In  this  experiment,  nitric  acid  was  liberated  from  one  of 
its  compounds  thus  :  — 

KN03  +  H2S04  =  HKS04  +  HNOs. 

Commercial  nitric  acid,  enormous  quantities  of  which  are 
consumed  annually,  is  obtained  by  treating  Chili  saltpetre, 
NaNO3,  with  sulphuric  acid  in  large  iron  retorts.  The 
vapors  of  nitric  acid  are  condensed  in  earthenware  con- 
densers. This  process  may  be  illustrated  in  the  laboratory 
by  means  of  the  apparatus  shown  in  Fig.  16.  One  method 
of  condensation  is  also  illustrated  by  the  experiment. 

EXP.  42.     Place  in  the  retort  A  (Fig.  16)  equal  parts,  by 
weight,  of  potassium  nitrate,  KNO3,  and  sulphuric  acid.     Sur- 


40  THE   NITROGEN    OXACIDS. 

round  the  receiver  R  with  snow  or  ice,  or  allow  a  stream  of 
cold  water  to  flow  over  it.  Heat  the  retort  gently,  when 
fumes  of  nitric  acid  will  be  given  off  and  condensed  in  the 
receiver  R. 

EXP.  43.  Heat  to  redness  some  powdered  charcoal  in  an 
iron  spoon,  and  then  cautiously  add  a  few  drops  of  the  nitric 
acid,  prepared  as  above.  Also  treat  a  fresh  portion  of  charcoal 
with  powdered  potassium  nitrate,  KN03. 

Nitric  acid  and  its  compounds  contain  much  oxygen, 
which  is  quite  readily  given  up  to  other  substances  under 
the  influence  of  heat.  Hence  both  the  acid  and  its  com- 
pounds are  called  oxidizing  agents. 


FIG.  16. 

/  Substances  containing  carbon  and  other  inflammable 
constituents  are  capable  of  burning  in  the  absence  of  air 
when  mixed  with  potassium  nitrate.  Hence  this  com- 
pound is  extensively  used  in  the  manufacture  of  gun- 
powder, which  is  simply  a  mechanical  mixture  of  sulphur, 
charcoal,  and  saltpetre.  Again,  gun-cotton  is  made  by 
treating  cellulose,  or  pure  vegetable  fibre,  with  a  mixture 
of  sulphuric  and  nitric  acids.  Nitro-glycerme  is  made  by 
treating  glycerine  with  the  same  acids. 


EXEKCISES.  41 

An  efficient  explosive  owes  its  power  to  the  large  volume 
of  gas  that  is  suddenly  liberated  during  its  combustion. 

Nitric  acid  unites  with  most  metals  to  form  a  class  of 
compounds  called  nitrates.  Now  these  nitrates  are  all 
soluble  in  water ;  hence  nitric  acid  is  largely  used  in  the 
laboratory  as  a  solvent.  In  the  arts  this  acid  also  finds 
many  important  uses. 

45.  Test  for  Nitric  Acid.  —  Make  a  mixture  of  the  sub- 
stance to  be  tested  with  a  solution  of  ferrous  sulphate, 
FeSO4,  in  a  test-tube.  Now  carefully  add  a  small  quan- 
tity of  sulphuric  acid,  without  mixing  with  the  contents 
of  the  tube.  The  sulphuric  acid  will  sink  to  the  bottom 
of  the  tube,  and  where  the  two  liquids  meet  a  brown  ring 
will  appear.  Sometimes  the  formation  of  the  ring  will  be 
aided  by  tapping  the  test-tube  lightly  with  the  finger.  If 
the  contents  of  the  tube  be  now  mixed,  the  ring  will  dis- 
appear and  the  solution  become  colorless. 

NOTE.  Bromides  and  iodides  will  give  nearly  this  same  test,  but  the 
solution  will  not  lose  so  much  of  its  color  when  shaken  when  either  of 
these  substances  is  present.  But  it  is  always  best  to  test  for  these  sub- 
stances, when  working  an  unknown,  before  reporting  nitric  acid. 

EXERCISES. 

(For  Revieio  or  Advanced  Course.) 

1.  How  many  grammes  of  laughing-gas  may  be  had  from  100&  NH4N03  ? 
If  one  litre  of  this  gas  at  0°  C.  and  760mm  pressure  weighs  1.972e,  how 
many  litres  of  this  gas  will  be  obtained  ? 

2.  By  adding  one  molecule  of  water  to  the  first,  third,  and  fifth  oxides 
of  nitrogen,  the  following  results  will  be  obtained :  — 

N2O  +  H20  =  2  HNO  ;   N203  +  H^  =  2  HNO2  ;   X2O3  +  H.,0  =  2  HNO3. 
What  acids  are  thus  produced  ?     Can  the  first  one  be  actually  produced 
in  that  way  ?     Oxides  which  behave  thus  are  called  Anhydrides.     Define 
anhydrides. 


42  EXERCISES. 

3.  The  specific  gravities  of  three  of  the  nitrogen  oxides  are  respectively 
1.527  ;  1.038  ;  1.5909.     What  are  the  corresponding  molecular  weights  of 
these  oxides,  and  what  their  molecular  formulae  ? 

4.  The  specific  gravities  hitherto  given  refer  to  air  as  the  standard,  or 
air  =  1.     Sometimes  hydrogen  is  used  as  the  standard.     Now  it  is  evident 
that  the  hydrogen  molecule,  H2,  weighs  twice  as  much  as  the  hydrogen 
atom.     Knowing  the  atomic  weights,  it  is  easy  to  find  the  density  (which 
is  numerically  equal  to  the  specific  gravity)  of  gases  when  referred  to 
the  hydrogen  unit.     Thus,   in  ammonia,   NH3,   the  molecular  weight  is 
14  +  3  =  17.     Now,  according  to  Avogadro's  hypothesis,  equal  volumes  of 
hydrogen  and  of  ammonia  under  like  conditions  contain  the  same  number 
of  molecules.     Whence  it  follows  that  if  hydrogen  be  taken  as  1,  the  den- 
sity of  ammonia  is  17-^2  =  8.5.     A  like  manner  of  reasoning  will  show 
that  the  density  of  any  gas  referred  to  the  hydrogen  unit  may  be  found 
by  dividing  the  molecular  weight  by  2.     Determine  the  densities  of  N20  ; 
N203 ;  N204. 

5.  Read  Remsen's  Theoretical  Chemistry,  pp.  32-38,  for  a  fuller  dis- 
cussion of  Avogadro's  hypothesis  and  the  determination  of  the  molecular 
weights  of  the  elements  and  of  compounds.     Also  see  Meyer's  Modern 
Theories  of  Chemistry,  pp.  7-17. 

6.  Write  a  sketch  of  the  chemist  Rutherford,  who  discovered  nitrogen 
in  1772. 

7.  How  many  grammes  of  ammonia  can  be  obtained  from  100s  of 
NH4C1  ? 

8.  Read  the  experiment  wherein  you  prepared  nitrogen.     Now,  why 
can  you  not  prepare  oxygen  from  the  air  by  using  some  substance  to 
combine  with  the  nitrogen  ? 

9.  Measure  the  laboratory,  and  calculate  its  cubic  contents.    Now,  if 
one  litre  of  air,  under  standard  conditions,  weighs  1.2932s,  how  much 
nitrogen  does  the  room  contain  ?     How  many  grammes  of  ammonia  would 
be  produced  if  the  whole  of  the  nitrogen  were  combined  with  hydrogen  ? 

10.  Determine  approximately  the  amount  of  nitrogen  in  a  given  volume 
of  air  thus  :  Make  a  small  wooden  saucer-shaped  boat,  and  on  it  place  a 
small  pile  of  fine  iron  filings  which  has  been  moistened  with  a  solution  of 
ammonium  chloride.     Now  float  the  boat  on  some  water  in  a  convenient 
vessel,  and  place  down  over  the  whole  a  tall  graduated  glass  jar.     Support 
the  jar  so  that  it  may  be  left  standing  for  a  few  days.     When  the  water 
ceases  rising  in  the  jar,  measure  the  volume  of  the  residual  gas,  and  make 
the  proper  computations.   The  iron  unites  with  the  oxygen,  and  thus  forms 
a  solid.     Test  the  residual  gas  for  nitrogen  by  means  of  a  burning  match. 


CHAPTER   IV. 

CHLORINE,   BROMINE,  IODINE,  AND   FLUORINE,  AND   THEIR 
•COMPOUNDS    WITH    HYDROGEN    AND    OXYGEN. 

DATA  FOR  COMPUTATIONS.  — CHLORINE  :  Symbol,  Cl ;  Molecular  Formula, 
Ci, ;  Atomic  Weight,  35.5  ;  Weight  of  I1  at  0°  C.  and  760mm,  3.173s.  — 
BROMINE  :  Symbol,  Br ;  Molecular  Formula,  Bra ;  Atomic  Weight,  80 ; 
Specific  Gravity  ( Water  =  1),  3.1872.  —  IODINE  :  Symbol,  I ;  Molecular 
Formula,  I2 ;  Atomic  Weight,  127  ;  Specific  Gravity  ( Water  =  1),  4.048. 
-  FLUORINE  :  Symbol,  F  ;  Atomic  Weight,  19. 

CHLORINE. 

46.  Occurrence.  —  Chlorine  never  occurs  free  in  nature, 
owing  to  its  intense  chemism  for  other  elements.     Its  com- 
pounds, however,  are  plentiful,  and  occur  in  large  quanti- 
ties.    The  most  important  compound  of  chlorine  is  sodium 
chloride,  or  common  salt,  NaCL     The  chlorides  of  potas- 
sium, calcium,  and  magnesium  also  occur  native,  but  in 
much  smaller  quantities  than  the  sodium  compound. 

47.  Preparation  and  Properties.  —  EXP.  44.     Place  a  mix- 
ture of  sodium  chloride,  NaCl,  and  manganese  dioxide,  Mn02, 
in  a  test-tube,  and  add  a  few  drops  of  sulphuric  acid.     Note 
the  gas  which  is  liberated,  and  hold  in  it  a  strip  of  moist  blue 
litmus  paper.     After  the  color  of  the  paper  has  disappeared, 
moisten  the  strip  in  ammonia,  and  note  that  the  color  cannot 
be  restored.     In  fact,  the  paper  is  bleached.    Also  try  to  bleach 
a  strip  of  moist  unbleached  cotton  cloth. 

Ex.     Try  to  obtain  chlorine  from  hydrochloric  acid  by  acting  upon  it 
\vith  manganese  dioxide,  MnO2.    Describe  the  experiment  in  detail. 

43 


44 


CHLOBINE. 


Chlorine  is  a  heavy,  greenish  yellow  gas,  possessing 
remarkably  active  chemical  properties.  It  was  discovered 
in  1774  by  Scheele.  It  is  extensively  used  for  bleaching 
purposes  and  in  the  manufacture  of  bleaching-powder 
(Art.  53).  It  seems  that  chlorine  in  the  presence  of 
moisture  is  capable  of  effecting  the  following  chemical 
reaction :  — 

2  Cl  +  H20  =  2  HC1  +  0. 

Now  the  oxygen  thus  liberated,  while  in  a  nascent  state  or 
at  the  instant  of  its  liberation,  possesses  a  stronger  chem- 
ism  than  when  in  its  ordinary  molecular  condition ;  thus  it 
is  enabled  to  combine  with  the  coloring-matter  and  destroy 
it.  It  may  be  well  to  note  in  this  connection  that  all 
elements  when  in  a  nascent  state  possess  far  more  active 
properties  than  when  in  their  ordinary  conditions. 

Chlorine  water  finds  many  useful  applications  in  the 
laboratory.  The  best  method  of  preparing  a  solution  of 

chlorine  in  water  is  illus- 
trated by  the  following 
experiment :  — 

EXP.  45.  In  the  generat- 
ing-flask  A  (Fig.  17)  place 
equal  weights  of  common 
salt  and  manganese  dioxide 
which  have  been  pulverized 
and  mixed.  To  this  mixture 
add  twice  its  weight  of  dilute 
sulphuric  acid,  consisting  of 
equal  weights  of  water  and 
FlG  17  acid.  Now  apply  a  gentle 

heat,  when  chlorine  gas  will 

be  given  off  abundantly.  The  wash-bottles  B  and  C,  which 
contain  simply  cold  water,  will  secure  the  desired  solution. 


CHLORINE.  45 

By  disconnecting  the  wash-bottles,  and  joining  instead  a  long 
glass  tube,  the  gas  may  be  delivered  at  the  bottom  of  a  tall 
glass  jar,  and  thus  collected  by  what  is  termed  "Displacement." 

The  reaction  which  takes  place  in  this  experiment  is  as 
follows  :  — 


2NaCl  +  Mn02+  3  H2S04=  2  NaHS04+  MnS04+  2  H20+  2  Cl. 

This  equation  is  a  typical  one,  since  bromine  and  iodine 
may  be  prepared  in  the  same  way  by  substituting  a  bro- 
mide or  an  iodide  for  the  chloride. 

In  testing  for  bromine  or  iodine,  chlorine  water  is  used 
to  liberate  these  elements  from  their  compounds.  Chlorine 
water,  as  prepared  in  Exp.  45,  will  answer  for  this  purpose, 
but  a  solution  of  chlorine  may  be  made  more  quickly  and 
more  conveniently  thus  :  — 

EXP.  46.  In  a  test-tube  place  a  few  crystals  of  potassium 
chlorate,  KC1O3?  and  add  sufficient  hydrochloric  acid  to  cover 
the  crystals  half  an  inch  deep.  Now  warm  the  contents  of 
the  tube  until  chlorine  is  escaping  freely,  when  the  tube  is  to 
be  filled  nearly  full  of  cold  distilled  water.  The  gas  is  dis- 
solved by  the  water.  The  reaction  is  :  — 

4  HC1  +  2  KC103  =  2  KC1  +  2  H20  +  C1204  +  2  Cl. 

The  compounds  KC1  and  C1204  are  dissolved  in  the  water,  as 
well  as  the  chlorine  gas,  but  they  do  not  impair  the  efficiency 
of  the  solution. 

Ex.  In  how  many  different  ways  have  you  prepared  chlorine  ?  Try 
the  effect  of  an  acid  upon  bleaching-powder.  The  goods  to  be  bleached 
are  drawn  through  a  tank  of  weak  acid  after  they  have  been  passed 
through  a  solution  of  the  bleaching-powder.  Why  ? 

48.  Test  for  Chlorine.  —  Free  chlorine  gas  may  be  recog- 
nized by  its  odor,  color,  and  its  bleaching  effects  upon 
organic  colors. 


46  CHLORINE   AND   HYDROGEN. 


CHLORINE    AND    HYDROGEN;     OR,   HYDROCHLORIC 
ACID,   HC1. 

49.  Occurrence,  —  Hydrochloric  acid  occurs  in  small  quan- 
tities in  volcanic  gases.     But  its  compounds,  the  chlorides, 
as  previously  noticed,  occur  in  great  quantities. 

50.  Preparation  and  Properties.  —  EXP.  47.     Place  a  small 
quantity  of  sodium  chloride,  Nad,  in  a  test-tube,  and  then  add 
a  few  drops  of  sulphuric  acid.     Note  the  fumes  that  are  given 
off  when  the  contents  of  the  tube  are  gently  warmed.     The 
reaction  is :  — 

NaCl  +  H2S04  =  NaHS04  +  HC1. 

Test  the  fumes  of  this  acid  with  a  moist  blue  litmus  paper. 
Will  ammonia  restore  the  color?  Is  hydrochloric  acid  a 
bleaching  reagent? 

Hydrochloric  acid  is  an  important  article  of  commerce, 
and  it  is  prepared  as  a  by-product  from  the  same  chemicals 
used  in  the  preceding  experiment  while  treating  salt  with 
sulphuric  acid  in  the  manufacture  of  soda  ash. 

EXP.  48.  Take  three  test-tubes,  and  into  the  first  put  a 
solution  of  silver  nitrate,  AgN03 ;  into  the  second,  a  solution 
of  mercurous  nitrate,  Hg2(N03)2 ;  and  into  the  third,  a  solution 
of  lead  acetate,  Pb(C2H3O2)2.  Now  to  each  of  these  tubes  add 
a  few  drops  of  hydrochloric  acid.  Note  the  heavy  white  pre- 
cipitates which  are  thrown  down  in  each  tube. 

Hydrochloric  acid  is  used  extensively  in  the  laboratory 
for  analytical  purposes,  as  exemplified  in  the  preceding 
experiment.  The  lead,  silver,  and  mercury  unite  with  the 
chlorine  of  the  hydrochloric  acid  to  form  the  insoluble 
chlorides  of  these  metals.  Now,  since  these  three  metals 
are  the  only  ones  that  thus  form  insoluble  chlorides,  they 


CHLORINE   AND    HYDROGEN.  47 

may  be  considered  as  forming  a  group  which  may  be  re- 
moved from  a  solution  containing  any  or  all  the  other 
metals.  From  this  use  of  hydrochloric  acid  it  is  often 
spoken  of  as  a  group  reagent.  Again,  since  most  of  the 
compounds  formed  by  hydrochloric  acid  are  soluble  in 
water,  this  acid  is  extensively  used  as  a  solvent. 

When  three  volumes  of  hydrochloric  acid  are  mixed  with 
one  volume  of  nitric  acid,  Aqua  Regia,  or  Nitro-Hydro- 
chloric  Acid,  the  most  powerful  solvent  known,  is  formed. 
This  compound  owes  its  efficiency  to  the  fact  that  it  fur- 
nishes large  quantities  of  nascent  chlorine  to  act  upon  the 
substance  to  be  dissolved.  Only  a  gentle  heat  should  be 
employed  while  using  this  solvent,  otherwise  the  chlorine 
will  be  driven  off  to  waste. 

It  has  appeared  in  the  last  experiment  that  hydrochloric 
acid  is  a  gas.  But  this  gas  is  soluble  in  water,  one  volume 
of  water  dissolving  505  volumes  of  the  gas.  The  acid  em- 
ployed for  various  purposes  is  a  solution  of  the  gas  in 
water.  Sometimes  this  acid  is  called  by  one  of  its  old 
names,  "Muriatic  Acid." 

51.  Test  for  Hydrochloric  Acid.  —  Hydrochloric  acid,  either 
free  or  in  any  of  its  combinations,  may  be  detected  by  add- 
ing to  the  solution  to  be  tested  a  few  drops  of  silver  nitrate, 
AgNO3.  If  hydrochloric  acid  be  present,  a  white  precipi- 
tate is  formed,  which  is  to  be  divided  into  two  parts.  To 
one  part  add  nitric  acid :  the  precipitate  does  not  dissolve. 
To  the  second  part  add  ammonia,  and  the  precipitate  will 
dissolve  readily. 

NOTE.  Since  the  precipitates  formed  with  silver  nitrate  by  the  bromides 
and  iodides  are  liable  to  be  mistaken  for  that  of  hydrochloric  acid,  the 
student  must  never  report  hydrochloric  acid  from  this  test  without  first 
testing  for  bromides  (Art,  59)  and  iodides  (Art.  64). 


48  CHLORINE   AND    OXYGEN. 


CHLORINE    AND    OXYGEN. 

52.  Chlorine  and  oxygen  unite  to  form  three  compounds, 
viz. :  — 

Chlorine  monoxide C120. 

Chlorine  trioxide C1203. 

Chlorine  tetroxide C1204. 

These  compounds  never  occur  in  nature,  and  have  not 
been  prepared  by  the  direct  union  of  chlorine  and  oxygen. 
They  are  unimportant,  and  dangerous  to  prepare,  owing  to 
their  liability  to  explode. 

CHLORINE,   OXYGEN,   AND    HYDROGEN;     OR,   THE 
CHLORINE    OXACIDS. 

53.  There  are  four  acids  in  this  series,  but  none  of  them 
are  of  importance  in  the  arts  or  in  commerce.     But  they 
serve  well  to  illustrate  some  principles  in  chemical  nomen- 
clature, as  will  appear  in  the  next  chapter.     The  names 
and  formulae  of  these  acids  follow :  — 

Hypochlorous  acid      ....  HC10. 

Chlorous  acid HC102. 

Chloric  acid HC103. 

Perchloric  acid HC104. 

The  salts  of  some  of  these  acids  are  of  importance. 
Thus,  hypochlorous  acid  unites  with  calcium  to  form 
bleaching-powder.  In  reality,  this  useful  compound  is 
manufactured  by  passing  chlorine  gas  into  large  chambers 
containing  slaked  lime,  when  the  following  reaction  is 
supposed  to  take  place  :  — 

2  Ca(OH)2  +  4  Cl  =  2  H,O  +  (CaCls  +  Ca(C10)2). 


CHLORINE,  OXYGEN,  AND  HYDROGEN.        49 

If  this  be  the  correct  explanation,  bleaching-powder  is  a 
mixture  of  calcium  chloride  and  calcium  hypochlorite. 

Chloric  acid  forms  a  class  of  compounds  that  are  some- 
what important,  —  the  chlorates.  Potassium  chlorate,  the 
most  useful  of  these  compounds,  is  prepared  by  passing 
chlorine  gas  into  a  warm  concentrated  solution  of  potas- 
sium hydroxide,  thus :  — 

6  Cl  +  6  KOH  =  5  KC1  +  3  H20  +  KC103. 

The  chlorates  are  liable  to  explode  when  brought  in  con- 
tact with  any  combustible  substance,  owing  to  the  ease 
with  which  they  give  up  oxygen.  It  is  not  safe  even  to 
grind  a  chlorate  in  a  mortar  with  a  combustible  substance. 
When  such  mixtures  are  to  be  made,  as  when  making 
colored  fires,  the  materials  must  be  ground  separately,  and 
carefully  mixed  afterwards  on  a  sheet  of  paper.  Some 
idea  of  the  behavior  of  the  chlorates  may  be  obtained  by 
the  following  experiment,  which  is  safe  if  carefully  con- 
ducted :  — 

EXP.  49.  Place  two  small  crystals  of  potassium  chlorate 
in  a  dry  iron  mortar.  Add  a  few  grains  of  dry  sugar.  Now 
wrap  a  towel  about  the  hand,  and  grasp  the  pestle  in  the 
towel.  Kub  the  material  in  the  mortar  lightly  until  a  good 
mixture  is  made,  and  then  strike  the  pestle  sharply  down  upon 
the  mixed  substances.  A  sharp  explosion  will  ensue.  If  sul- 
phur, gum  shellac,  or  any  combustible  substance  be  used  in 
place  of  the  sugar,  an  explosion  will  occur. 

54.  Test  for  Chloric  Acid  or  the  Chlorates.  —  A  chlorate, 
when  treated  with  hydrochloric  acid  in  a  test-tube,  will 
yield  free  chlorine  gas  (Exp.  46).  Further,  if  a  few  crys- 
tals of  a  chlorate  be  placed  in  a  test-tube,  and  sulphuric 
acid  be  added,  a  sharp  explosion  will  follow. 


50  BROMINE. 

NOTE.  In  making  this  test,  a  bit  of  cloth  should  be  put  around  the 
tube,  and  the  cloth  is  to  be  taken  firmly  in  a  pair  of  pincers.  Thus  the 
tube  may  be  held  firmly,  and  its  mouth  must  not  be  pointed  towards  any 
apparatus  or  in  the  direction  of  any  person  in  the  room. 


BROMINE. 

55.  Occurrence.  —  Bromine  never  occurs  free  in  nature. 
It  is  chiefly  obtained  from  the   mother  liquor  remaining 
after  removing  the  crystals  of  common  salt  in  salt  factories. 
Balard  discovered  bromine  in  the  year  1826,  in  sea-water. 
Bromine  is  an  article  of  .commerce,  but  it  is  by  no  means 
a  plentiful  element. 

56.  Preparation  and  Properties.  —  EXP.  50.     Place  a  mix- 
ture  of   potassium   bromide,   KBr,    and    manganese   dioxide, 
Mn02,  in  a  test-tube,  and  add  a  few  drops  of  sulphuric  acid. 
Note  the  heavy  dark-colored  fumes  given  off. 

Ex.  Using  the  equation  under  Exp.  45  as  a  model,  and  substituting 
KBr  for  NaCl,  write  out  the  reaction  which  occurs  in  this  experiment. 
For  the  method  of  preparing  bromine  water  and  liquid  bromine,  see 
Shepard's  Elements,  p.  109. 

Bromine  is  a  dark-colored  liquid  at  ordinary  tempera- 
tures, which  always  gives  off  pungent,  irritating  fumes. 
It  is  used  to  some  extent  as  a  disinfectant,  but  it  is  not  so 
energetic  in  its  action  in  this  respect  as  chlorine. 

Bromine  of  commerce  is  prepared  by  the  action  of  chlo- 
rine on  its  compounds.  The  chlorine  is  generated  in  the 
mother  liquor  by  means  of  the  chemicals  employed  in 
Exp.  44. 

57.  Test  for  Free  Bromine.  —  Free  bromine,  even  in  dilute 
solutions,  when  shaken  in  a  test-tube  with  carbon  disul- 
phide,  CS2,  colors  the  disulphide  brownish  red. 


BROMINE,    HYDROGEN,    AND   OXYGEN.  51 


BROMINE,    HYDROGEN,    AND    OXYGEN. 

58.  The  compounds  of  bromine  with  oxygen  and  hydro- 
gen closely  resemble  those  of  chlorine.     Thus  we  have  — 

Hydrobromic  acid HBr. 

Hypobromous  acid     ....  HBrO. 

Bromic  acid HBr03. 

Perbromic  acid HBrO4. 

None  of  the  oxides  of  bromine  have  been  prepared. 
None  of  these  compounds,  except  hydrobromic  acid,  are 
of  importance ;  and  of  the  compounds  formed  by  them,  the 
bromides  corresponding  to  the  acid,  HBr,  are  the  only 
ones  much  used  in  the  arts.  Thus,  potassium  bromide, 
KBr,  is  used  in  medicine ;  silver  bromide,  AgBr,  is  used 
in  photography ;  while  magnesium  bromide,  MgBra,  occurs 
in  some  mineral  waters.  Hydrobromic  acid  itself  is  used 
to  some  extent  in  organic  analysis. 

59.  Test  for  Hydrobromic  Acid  or  the  Bromides.  —  Place 
the  solution  to  be  tested  in  a  test-tube,  and  add  a  small 
quantity  of  chlorine  water,  to  liberate  the  bromine.     Now 
add  a  few  drops  of  carbon  disulphide,  CS2,  and  shake  the 
contents  of  the  tube  thoroughly.     If  the  substance  tested 
be  hydrobromic  acid  or  any  of  its  compounds,  the  carbon 
disulphide  will  be  colored  brownish  red  by  the  free  bromine 
liberated  by  means  of  the  chlorine  water. 

IODINE. 

60.  Occurrence.  — Iodine  never  occurs  free  in  nature.     It 
is  mostly  obtained  from  sea-water,  from  which  it  is  taken 
up  by  sea-weeds.     These  weeds  are  gathered  along  the 


52  IODINE. 

coasts  of  some  countries,  especially  Ireland  and  Scotland, 
where  they  have  been  washed  up  by  storms.  The  weeds 
are  then  dried,  and  burned  in  shallow  trenches  at  a  low 
temperature,  so  that  the  iodides  of  sodium,  potassium,  etc., 
may  not  be  volatilized.  Now  these  iodides  are  soluble 
in  water,  so  they  are  removed  from  the  "kelp,"  as  the 
ashes  of  the  plants  are  popularly  called,  by  solution  in 
water. 

Plantations  of  these  weeds  are  cultivated  in  some  parts 
of  the  ocean,  and  at  proper  times  vessels  are  sent  out  to 
gather  the  weeds. 

Again,  a  considerable  portion  of  the  iodine  that  now 
comes  to  market  is  obtained  from  sodium  iodide,  Nal, 
found  occurring  along  with  Chili  saltpetre. 

61.  Preparation  and  Properties.  —  EXP.  51.     Place  a  mix- 
ture of  potassium  iodide,  KI,  and  manganese  dioxide,  Mn02, 
in  a  test-tube,  and  add  a  small  quantity  of  sulphuric  acid. 
Note  the  vapors  evolved. 

Ex.  Compare  this  method  of  preparing  iodine  with  the  processes  used 
in  obtaining  chlorine  and  bromine,  and  write  the  reaction. 

Commercial  iodine  is  prepared  by  the  method  given  in 
the  preceding  experiment.  The  materials  are  placed  in 
iron  retorts,  and  the  vapors  of  iodine  are  condensed  in  black, 
shining  crystals  upon  the  sides  of  suitable  condensers. 

Iodine  is  much  used  in  medicine,  especially  in  reducing 
swellings  and  in  checking  the  spread  of  eruptive  diseases 
like  erysipelas.  When  thus  applied,  it  is  brought  into 
solution  by  dissolving  20  parts  of  iodine  with  30  parts  of 
potassium  iodide  in  900  parts  of  water. 

62.  Test  for  Free  Iodine.  —  Free  iodine  colors  carbon  di- 
sulphide,  CS2,  violet. 


IODINE   AND   ITS   COMPOUNDS.  53 


IODINE   AND   ITS   COMPOUNDS  WITH   HYDROGEN  AND 

OXYGEN. 

63.  The    compounds   formed   by  iodine   resemble   very 
closely  those  formed  by  chlorine  and  bromine.     This  will 
appear  by  inspecting  the  formulae  of  the  following  com- 
pounds :  — 

Hydriodic  acid HI. 

Iodine  pentoxide I205. 

lodic  acid HI03. 

Periodic  acid HIO4. 

None  of  these  compounds  are  used  excepting  hydriodic 
acid,  which  has  a  limited  application  in  analytical  work. 
None  of  the  compounds  formed  by  these  substances  and 
the  metals  are  of  importance  excepting  potassium  iodide, 
KI.  This  is  much  used  in  medicine  as  a  sedative. 

64.  Test  for  Hydriodic  Acid  or  an  Iodide.  —  Add  chlorine 
water  to  the  substance,  in  order  to  liberate  iodine.    Now  add 
to  the  solution  a  few  drops  of  carbon  disulphide,  and  shake 
the  contents  of  the  tube  thoroughly.    If  this  acid  or  one  of 
its  compounds  be  present,  the  disulphide  is  colored  violet. 

NOTK.  The  iodides  give  a  precipitate  with  silver  nitrate,  which  may  be 
mistaken  for  that  of  chlorine  or  bromine.  See  Art.  61. 


FLUORINE. 

65.  Fluorine  is  a  gaseous  element  which  has  but  recently 
been  prepared.  It  was  obtained  by  electrolyzing  perfectly 
dry  hydrofluoric  acid,  HF,  in  platinum  tubes.  Its  chief 
compound  is  with  calcium,  as  found  in  the  mineral  fluor- 
spar, CaF2.  Fluorine  forms  no  compounds  with  oxygen, 


54  EXERCISES. 

and  but  one  with  hydrogen,  hydrofluoric  acid,  HF.  This 
acid  possesses  the  remarkable  power  of  combining  with  glass. 
It  may  be  prepared  by  acting  on  fluor-spar  with  sulphuric 
acid :  -  CaF2  +  H2SO4  =  CaS04  +  2  HF. 

The  preparation  and  behavior  of  this  acid  may  be  shown 
by  the  following  experiment :  — 

EXP.  52.  Cover  both  sides  of  a  sheet  of  glass  with  a  coating 
of  beeswax.  With  a  sharp,  soft  point  cut  through  the  wax  some 
design  or  some  written  characters.  Now  place  some  powdered 
fluor-spar  in  an  evaporating-dish,  and  then  pour  on  enough  sul- 
phuric acid  to  cover  the  fluor-spar.  Support  the  glass  a  short 
distance  above  the  dish,  and  warm  the  contents  of  the  dish 
gently.  Keep  the  whole  apparatus  where  the  fumes  will  not 
escape  in  the  room,  and  in  a  short  time  the  design  or  writing 
will  be  etched  into  the  glass.  This  is  best  seen  when  the  wax 
is  removed.  The  fumes  of  hydrofluoric  acid  are  poisonous, 
and  must  not  be  inhaled. 

What  takes  place  may  be  shown  by  this  equation :  — 
Si02  +  4  HF  =  2  H2O  +  SiF4. 

Glass  is  a  compound  of  sand,  SiO2,  and  metals,  usually 
sodium  or  potassium.  The  silicon  tetrafluoride,  SiF4,  is 
a  gas  which  escapes  as  fast  as  formed :  the  fumes  may  be 
seen  during  the  experiment. 

The  best  test  for  fluorine  is  the  etching  test,  as  shown 
in  the  preceding  experiment. 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  Make  a  table  showing  the  atomic  weights  and  physical  conditions  at 
ordinary  temperatures  of  chlorine,  bromine,  and  iodine.  Also  make  a 
table  showing  the  formulae  of  their  compounds  with  hydrogen  and  oxygen. 
What  similarities  and  what  differences  do  you  find  ? 


EXERCISES.  55 

2.  Which    possesses    the    stronger  chemism,   chlorine    or  bromine  ? 
Chlorine  or  iodine  ?     (Sue.    See  the  tests  for  bromine  and  iodine.) 

3.  How  many  grammes  of  chlorine  may  be  obtained  from  1008  NaCl  ? 
How  many  litres  would  this  make  under  standard  conditions  ? 

4.  The  volume  of  a  given  mass  of  any  gas  varies  according  to  the  tem- 
perature in  the  ratio  of  273  +  t  :  273  -f  tf,  in  which  t  is  the  given  tempera- 
ture, and  t'  the  required  temperature.    Now  let  V  be  the  given  volume, 
and  V  the  required  volume,  and  we  have  the  proportion  :  — 

F:  V  :  :  273  +  t  :  273  +  t'. 

By  suitable  transformations  this  proportion  gives  an  equation  suitable  for 
solving  problems  concerning  gases  in  which  variations  of  temperature  are 
involved  :  — 

CD         F     =      ^ 
273  +  t     273  +  t1 

Solve  the  following  problem  :  — 

PROBLEM.     5l  of  chlorine  gas  at  15°  C.  become  how  many  litres  at 
20°  C.? 

5.  The  volume  of  a  given  mass  of  gas  varies  inversely  as  the  pressure 
or  height  of  the  barometer.    Letting  H  be  the  given  height  of  the  barom- 
eter, and  H'  the  required  height,  we  have  this  proportion  :  — 

F:  V  :  :  H'  :  H. 

This  gives  the  equation  — 

(2)      VH=  VH', 

an  equation  useful  in  solving  problems  in  gases  involving  variations  in 
pressure.  Solve  this 

PROB.     101  of  oxygen  gas  under  760™™  pressure  become  how  many 
litres  under  758mm  ? 

6.  By  combining  equations  (1)  and  (2),  we  have  :  — 

(3) 


273  +  t     273  +  t' 

This  equation  is  used  when  both  temperature  and  pressure  vary.     Solve 
this 

PROB.  The  barometer  reads  755mm  and  the  thermometer  15°  C.  when 
101  of  hydrogen  gas  were  generated  ;  how  many  litres  will  this  hydrogen 
become  when  the  pressure  is  762mm  and  the  temperature  18°  C.? 

7.  "What  per  cent  of  KBr  is  bromine  ?     Potassium  ?     Give  a  rule  for 
determining  the  percentage  composition  of  any  chemical  compound. 

8.  How  much  silver  nitrate  would  be  required  to  precipitate  the  chlorine 


56  EXERCISES. 

in  108  of  sodium  chloride  ?  (Suo.  AgNO3  +  NaCl  =  AgCl  +  NaNO3.  By 
taking  the  molecular  weights  of  these  compounds,  we  find  that  170s  of 
AgN03  will  precipitate  the  chlorine  in  58.5s  of  NaCl.)  How  much  AgCl 
will  be  produced  ?  How  much  NaNO3  ? 

9.  WRITING  EQUATIONS.  It  is  desirable  to  know  how  to  write  equa- 
tions. This  may  be  understood  from  the  following  explanation  :  Place 
the  formulae  of  the  known  substances,  or  the  substances  to  be  experi- 
mented upon,  in  the  first  member  of  the  equation,  and  connect  them  by 
the  sign  +.  Now  determine  (by  experiment  or  otherwise)  what  sub- 
stances are  produced,  and  write  their  formulae  in  the  second  member, 
and  connect  them  also  by  the  sign  +.  If  the  equation  now  balances,  it 
is  complete.  If  not  balanced,  this  rule  applies :  There  must  be  an  equal 
number  of  atoms  of  each  element  in  both  members  of  the  equation.  For 
example,  take  the  reaction  between  H2SO4  and  KN03.  Since  these  sub- 
stances are  known,  we  commence  the  equation  thus  :  — 

H2SOi+KNO3= 

Experiment  has  shown  that  under  certain  conditions  HN()3  and  K2S04 
are  produced.  Therefore  we  place  these  formulae  in  the  second  member, 
and  our  equation  reads  :  — 

H2SO4  +  KN03  =  K2S04  +  HN03. 

By  inspection,  it  appears  that  the  hydrogen  atoms  do  not  balance,  so  we 
multiply  the  HNO3  by  2.  Again,  the  potassium  atoms  do  not  balance,  so 
we  multiply  KNO3  by  2,  and  the  equation  now  balances,  and  reads  :  — 

H2SO4  +  2  KN03  =  K2SO4  +  2  HN03. 

Form  equations  from  these  data :  — 

1.  When  BaCl2  and  K2SO4  react,  BaS04  and  KC1  are  produced. 

2.  When  Hg2(N03)2  and  HC1  react,  Hg2Cl2  and  HN03  are  produced. 


CHAPTER  V. 

BINARY  COMPOUNDS  ;  HIGHER  COMPOUNDS  ;  ACIDS,  BASES, 
SALTS  ;  ACID  AND  NORMAL,  SALTS  ;  VALENCE  '  DETERMI- 
NATION OF  ATOMIC  WEIGHTS  :  CHEMICAL  NOMENCLA- 
TURE ;  ETC. 

66.  Binary  Compounds.  —  We  have  now  studied  a  num- 
ber of  chemical  compounds,  and  it  will  be  profitable  to  con- 
sider these  substances  from  a  theoretical  standpoint  before 
proceeding  farther,  for  the  purpose  of  arranging  them  in 
classes  and  of  explaining  some  of  the  principles  of  chemi- 
cal nomenclature. 

We  have  had  a  number  of  substances  like  H2O,  HC1, 
HI,  HBr,  HF,  etc.,  which  consist  of  but  two  elements  com- 
liined  in  definite  proportions.  Now  these  substances,  and 
all  others  which  consist  of  but  two  elements,  are  called 
Binary  Compounds.  The  principal  elements  which  form 
binary  compounds  are  oxygen,  sulphur,  chlorine,  bromine, 
and  iodine. 

It  is  a  general  rule  that  the  names  of  all  binary  com- 
pounds shall  end  in  "  ide."  Thus  the  binary  compounds 
containing  oxygen  are  called  oxides,  while  the  names  sul- 
phides, chlorides,  iodides,  etc.,  readily  suggest  what  element 
enters  into  the  compound  named. 

Now,  since  any  of  the  "  ide  "-forming  elements  may 
unite  with  any  of  the  metals  to  form  an  "  ide  "  compound, 
it  is  necessary  to  distinguish  between  the  compounds  thus 
formed.  This  is  done  by  prefixing  the  name  of  the  metal 

57 


58  BINARY  COMPOUNDS. 

to  that  of  the  "  ide  "-forming  element.  Thus,  KC1  is  called 
potassium  chloride,  NaBr  is  called  sodium  bromide,  CaF2 
is  called  calcium  fluoride,  etc. 

Sometimes  an  "  ide  "-forming  element  unites  in  more 
than  one  proportion  with  another  element.  In  such  cases 
the  prefixes  "  mon,"  "  di,"  "  tri,"  "  tetr,"  "  pent,"  etc.,  sig- 
nifying respectively  one,  two,  three,  four,  five,  etc.,  are 
prefixed  to  the  name  of  the  "  ide "-  forming  element. 
Thus  we  have  chlorine  monoxide,  C12O ;  chlorine  trioxide, 
C12O3 ;  etc.  The  nitrogen  oxides  also  furnish  further 
examples. 

Ex.  Student  name  the  following :  CaO ;  I2O5 ;  SiF^  ;  KF  ;  HBr ; 
CaS:  LiCl:  NaBr. 

There  are  some  of  the  metals  which  form  two  classes  of 
compounds.  In  such  cases  the  name  of  the  metal  is  mod- 
ified by  the  suifixes  "  ous "  and  "  ic."  Thus  we  have 
Hg2Cl2,  mercurous  chloride,  and  HgCL,  mercuric  chloride. 
The  principal  metals  forming  such  distinct  classes  are  mer- 
cury, iron,  copper,  tin,  and  lead.  Examples  of  these  will 
appear  further  on  in  their  appropriate  places. 

When  more  than  two  classes  of  compounds  are  formed, 
other  means  of  distinguishing  them  are  employed.  Thus 
manganese  forms  the  oxides  MnO,  manganous  oxide ; 
Mn2O3,  manganic  oxide  :  Mn3O4,  manganoso  -  manganic 
oxide,  i.e.  consisting  of  manganous  and  manganic  oxides ; 
and  MnO2,  manganese  dioxide. 

Sometimes  the  relation  of  2  to  3  is  indicated  by  the 
word  "  sesqui  "  ;  thus,  Fe2O3,  sesqui-oxide  of  iron.  But  the 
most  recent  name  for  this  compound  is  ferric  oxide.  It 
will  be  noticed  that  in  the  cases  of  iron,  copper,  tin,  lead, 
and  some  other  metals,  the  Latin  names  are  used  when 
naming  the  two  classes  of  salts. 


Acros.  59 

67.  Higher  Compounds  are  those  containing  more  than 
two  elements  combined  in  definite  proportions.    Examples 
of  these  are  already  familiar  to  the  student. 

68.  Acids,  —  In  the  preceding  pages  the  word  acid  has 
been  used  many  times,  and  several  acids  have  been  pre- 
pared and  tested.    It  is  difficult  to  give  a  concise  definition 
of  an  acid,  but  in  general  we  may  say  that  it  is  a  hydrogen 
compound  usually  having  a  sour  taste  and  corrosive  prop- 
erties ;  it  is  capable  of  changing  vegetable  colors,  as  in 
turning  blue  litmus  red  ;  and  it  can  give  up  some  or  all  of 
its  hydrogen  and  take  a  metal  instead. 

There  are  both  binary  and  higher  acids.  The  principal 
binary  acids  have  already  been  studied.  Thus  we  have 
had  HC1,  hydrochloric  acid,  or  hydrogen  chloride  ;  HBr, 
hydrobromic  acid,  or  hydrogen  bromide  ;  etc.  We  shall 
also  see  that  sulphur  and  some  other  elements  form  with 
hydrogen  binary  acids.  This  class  of  acids  is  often  called 
the  hydrogen  acids,  or  the  hydracids,  to  distinguish  them 
from  the  higher  acids,  which  contain  oxygen. 

We  have  also  had  experience  with  a  goodly  number 
of  the  higher,  or  better,  the  oxygen  acids.  Thus,  HNOg, 
nitric  acid;  HC1O3,  chloric  acid;  HBrOg,  bromic  acid;  etc. 
In  naming  these  acids,  it  is  a  rule  that  the  most  common, 
the  most  important,  or  the  one  first  discovered,  shall  have 
a  name  ending  in  "  ic,"  and  that  this  suffix  shall  be  joined 
to  the  name  of  the  acid-forming  element,  thus  :  — 


Nitric  acid, 
Chloric  acid,  HC103, 
Sulphuric  acid,  H2S04,  etc. 

The  acid  having  one  less  atom  of  oxygen  than  the  "  ic  " 
acid  has  "  ous  "  prefixed  to  the  name  of  the  acid-forming 


60  BASES.  —  SALTS. 

element ;  the  acid  with  one  less  atom  of  oxygen  than  the 
"  ous  "  acid  is  called  the  "  hypo-ous  "  acid ;  while  that  with 
one  atom  of  oxygen  more  than  the  "  ic  "  acid  is  called  the 
"  per-ic  "  acid.  All  this  will  become  apparent  by  an  exam- 
ination of  the  formulae  of  the  chlorine  oxacids. 

When  more  acids  than  those  just  enumerated  appear  in 
a  series,  other  means  of  naming  them  are  employed,  as  will 
become  apparent  in  the  sulphur  oxacids. 

69.  Bases.  —  The  word  base  is  used  differently  by  differ- 
ent chemists.     Some  define  a  base  as  being  any  substance 
that  will  unite  with  an  acid,  to  remove  part  or  all  of  the 
hydrogen  of  that  acid,  and  to  form  a  substance  called  a 
salt.     This  is  a  sweeping  definition,  and  would  include  at 
least  three   different  classes  of  substances,  viz. :    (1)  the 
metals  ;  (2)  the  metallic  oxides  ;  (3)  the  hydroxides,  which 
are  compounds  of  the  metals  and  the  radical  hydroxyl,  OH. 
As  examples  of  the  hydroxides,  we  may  mention  potassium 
hydroxide,    KOH ;    sodium   hydroxide,    NaOH ;    calcium 
hydroxide,  Ca(OH)2;   barium  hydroxide,  Ba(OH)2;   etc. 
Many  chemists  apply  the  word  base  to  the  hydroxides  only. 

70.  Salts.  —  When  an  acid  and  a  base  react,  the  acid  parts 
with  all  or  a  part  of  its  hydrogen,  and  forms  a  compound 
called  a  salt.     Thus,  when  a  metal  like  zinc  reacts  with 
hydrochloric  acid,  the  hydrogen  of  the  acid  is  set  free,  and 
the  salt,  zinc  chloride,  is  produced  thus  :  — 

Zn  +  2  HC1  =  ZnCl2  +  2  H. 

This  is  generally  true  of  acids  and  metals,  with  a  few 
exceptions.  Nitric  acid  forms  an  important  exception, 
since  under  ordinary  conditions,  while  salts  called  nitrates 
are  formed,  no  hydrogen  is  liberated,  but,  instead,  water, 


NORMAL,    ACID,    AND   BASIC    SALTS.  61 

H2O,  and  nitrogen  dioxide,  NO,  are  produced.    The  follow- 
ing equation  is  a  typical  one  for  nitric  acid  and  a  metal  :  — 

3  Cu  +  8  HN03  =  3  Cu(N03)2  +  4  H2O  +  2  NO. 

When  an  oxide  and  an  acid  react,  a  salt  and  water  are 
produced,  thus  :  — 

BaO  +  H2S04  =  BaS04  +  H2O. 

When  the  reaction  is  between  a  hydroxide  and  an  acid, 
a  salt  and  water  are  also  formed  :  - 

KOH  +  HC1  =  KC1  +  H20. 

Thus  it  appears  that  a  fair  definition  of  a  salt  would  be  : 
A  salt  is  an  acid  in  which  all  or  a  part  of  its  hydrogen  has 
been  replaced  by  a  metal. 

71.  Normal,  Acid,  and  Basic  Salts.  —  When  all  of  the 
hydrogen  of  an  acid  has  been  replaced  by  a  metal,  a 
normal  salt  is  obtained  ;  thus,  K2SO4,  potassium  sulphate, 
is  a  normal  salt.  When  only  a  part  of  the  hydrogen  has 
thus  been  replaced,  an  acid  salt  is  produced  ;  thus,  HKSO4, 
acid  potassium  sulphate,  is  an  acid  salt. 

An  oxide  or  a  hydroxide  of  a  metal  may  unite  with  a 
normal  salt  to  form  a  basic  salt.  Thus  :  — 


In  this  case  basic  mercuric  sulphate  is  formed.     Again  :  — 

Pb(N03)2  +  Pb(OH)2  =  2  PbOHN03. 
Water  may  also  produce  a  basic  salt  thus  :  — 

Bi(N03)3  +  2  H20  =  Bi(OH)2N03  +  2  HN03. 

We  will  now  explain  how  the  salts  derived  from  the 
different  acids  are  named.  In  the  case  of  the  salts  from 
the  binary  acids  what  has  been  said  under  binary  com- 


62  VALENCE. 

pounds  will  apply,  and  no  further  explanation  is  neces- 
sary. But  when  we  come  to  the  salts  from  the  oxacids, 
further  explanation  is  necessary. 

It  is  a  rule  that  when  the  name  of  the  oxacid  ends  in 
u  ic,"  the  name  of  the  salt  shall  end  in  "  ate  "  ;  and  when 
the  acid  ends  in  "  ous,"  the  salt  shall  end  in  "  ite."  This 
will  be  understood  by  examining  the  potassium  salts  of 
the  chlorine  oxacids,  as  follows  :  — 

Hypochlorous  acid,  HC10,  forms  potassium  hypochlorite,KC10. 
Chlorous  acid,  HC102,  forms  potassium  chlorite,  KC102. 
Chloric  acid,  HC103,  forms  potassium  chlorate,  KC103. 
Perchloric  acid,  HC104,  forms  potassium  perchlorate,  KC104. 

In  naming  the  acid  salts  it  is  best  to  indicate  the  number 
of  atoms  of  the  metal  present  by  the  usual  prefixes.  Thus, 
sodium  and  phosphoric  acid  form  two  acid  salts,  NaH2PO4, 
monosodium  phosphate,  and  Na2HPO4,  disodium  phosphate. 
The  normal  salt  is  called  simply  sodium  phosphate,  Na3PO4. 

72.  Valence.  —  Let  us  examine  the  following  f ormulse  : 
HC1 ;  H2O  ;  H3N ;  H4C.  Now  these  actually  represent  com- 
pounds, and  in  them  we  see  that  chlorine,  oxygen,  nitrogen, 
and  carbon  differ  in  the  number  of  hydrogen  atoms  that 
each  holds  in  combination.  This  is  explained  by  saying 
that  each  of  the  elements  named  has  a  different  valence. 
In  order  to  measure  the  valence  of  an  element,  we  may 
take  a  simple  atom  like  the  hydrogen  atom.  Let  this  be 
the  standard,  and  it  follows  that  chlorine  is  univaleiit, 
oxygen  is  bivalent,  nitrogen  is  trivalent,  and  carbon  is 
tetravalent.  If  we  wish  to  measure  the  valence  of  an  ele- 
ment that  does  not  unite  with  hydrogen,  we  may  take 
some  other  univalent  element,  like  chlorine,  which  does 
unite  with  the  element  in  question. 


SUBSTITUTING   POWER    AND    VALENCE.  63 

It  must  not  be  inferred  that  valence  is  an  unvarying 
property,  since  many  elements  appear  to  have  different 
valences  in  different  compounds.  Thus,  in  HC1  chlorine  is 
univalent,  while  in  HC1O3  it  is  pentavalent.  Likewise, 
phosphorus  in  PC13  is  trivalent,  while  in  PC15  it  is  pentav- 
alent. The  most  common  valences  of  the  elements  are 
indicated  in  the  table,  Art.  10,  by  small  Roman  numerals 
or  by  indices  written  to  the  right  and  above  the  symbol. 
Usually  the  symbols  are  written  without  these. 

73.  Substituting  Power  and  Valence.  —  We  have  already 
noticed  how  the  hydrogen  of  an  acid  is  replaced  by  a  metal 
to  form  a  salt.     This  replacement  takes  place  according  to 
fixed  laws,  depending  upon  the  valence  of  the  metal.    Thus 
a  univalent  metal  will  replace  one  atom  of  hydrogen,  a 
bivalent  metal  will  replace  two  atoms  of  hydrogen,  etc. 
If  the  acid  molecule  does  not  contain  a  sufficient  number 
of  hydrogen  atoms  to  equal  the  valence  of  the  metal,  the 
acid  must  be  multiplied  by  some  figure  to  make  them  equal. 
Thus,  Ca"  is  bivalent ;  when  it  unites  with  HNO3,  the  acid 
must  be  multiplied  by  2  in  order  to  satisfy  the  require- 
ments of  the  bivalent  calcium.      Ca(NO3)2  is  produced. 
Other  cases  arise,  but  they  will  offer  no  difficulty. 

74.  Determination  of  Atomic  Weights  by  Avogadro's  Hypoth- 
esis. —  Elements  that  form  compounds  that  are  gases  or 
may  be  converted  into  gases  may  have  their  atomic  weights 
determined  by  means  of  Avogadro's  hypothesis.     First  the 
molecular  weight  of  each  available  compound  of  that  ele- 
ment is  ascertained.     Then   each  compound  is  analyzed, 
and  the  proportions  noted  in  which  its  constituents  com- 
bine.    Then  the  smallest  number  which  occurs  in  any  of 
the  compounds  analyzed  is  taken  as  the  atomic  weight. 


64  EXERCISES. 


EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  If  to  the  number  which  represents  the  valence  of  an  element  we 
assign  a  positive  or  negative  sign,  the  sum  of  these  numbers  in  any  stable 
chemical  compound  will  always  equal  0,  provided  we  let  H  =  +  1,  O  =  —  2  ; 
and  the  metals  are  to  be  assigned  +  indices,  except  such  as  form  binary 
compounds  with  hydrogen. 

These  data  may  be  utilized  to  determine  the  valence  of  an  element  in 
any  compound  ;  e.g.  What  is  the  valence  of  Cl  in  HC1O4  ?  Now  H  =  +  1 
and  O4  —  —8.  What  is  needed  to  add  to  the  + 1  to  make  a  number  suf- 
ficiently great  so  that  when  it  is  added  to  a  —  8,  the  sum  shall  be  0  ?  That 
number  is  evidently  -f  7,  which  equals  the  valence  of  Cl  in  this  particular 
compound. 

Ex.     Determine  the  valence  of  chlorine  in  all  its  oxacids. 

2.  Many  chemists  prefer  to  write  what  are  called  molecular  equations. 
Most  of  those  already  given  are  what  might  be  termed  atomic  equations, 
since  they  are  supposed  to  indicate  what  takes  place  when  the  elements 
of  a  molecule  are  torn  apart  and  thus  brought  into  the  atomic  or  nascent 
state.     But  atoms  probably  do  not  remain  in  this  state,  but  immediately 
seek  out  other  atoms  with  which  they  may  unite  to  form  new  molecules. 
When  a  simple  gas  like  hydrogen  or  oxygen  is  liberated,  the  hydrogen 
atoms  unite  to  form  hydrogen  molecules ;  thus,  H  +  H  =  H2.     So,  like- 
wise, with  oxygen  or  any  element.     Molecular  equations,  then,  represent 
what  has  taken  place  after  this  re- arrangement  is  effected.    In  writing  mo- 
lecular equations  it  is  only  necessary  to  have  each  free  gaseous  element 
appear  as  a  molecule ;  thus  K  +  H2O  =  KOH  +  H  is  written  2  K  +  2  H2O 
=  2  KOH  +  Hj. 

Ex.  Rewrite  in  molecular  equations  all  suitable  atomic  equations 
previously  given.  Read  Meyer's  Modern  Theories  of  Chemistry,  pp. 
195-204. 


CHAPTER   VI. 

CARBON  AND   SOME   OF   ITS   COMPOUNDS  WITH  HYDROGEN, 
OXYGEN,  AND   NITROGEN. 

CARBON. 

DATA   FOR   COMPUTATIONS.  —  Symbol,  C  ;   Atomic  Weight,  12 ;   Specific 
Gravity:  Diamond,  3.5  to  3.6;  Graphite,  2.25;  Charcoal,  1.57. 

75.  Occurrence.  —  Carbon  occurs  widely  distributed.     In 
the  free  condition  it  is  found  in  transparent  crystals  as 
Diamonds,  and  in  opaque,  six-sided  slabs  as  Graphite.     In 
impure  forms  it  constitutes  the  greater  portion  of  Coal, 
Soot,  and  Lampblack.    But  the  largest  quantities  of  carbon 
are  found  combined  with  hydrogen,  oxygen,  nitrogen,  and 
a  few  other  elements,  in  plants,  and  in  all  living  structures. 
Again,  large  quantities  of  carbon  occur  in  the  carbonates 
and  in  carbon  dioxide. 

76.  Preparation  and  Properties.  —  EXP.  53.    Ignite  a  match, 
and  hold  in  the  flame  a  bit  of  cold  glass.     What  is  deposited 
on  the  glass  ?     Extinguish  the  match,  and  dip  the  glowing 
coal  in  water.   What  kinds  of  carbon  have  you  thus  prepared  ? 
Where  is  soot  deposited  ? 

Lampblack  is  prepared  on  the  large  scale  by  burning 
resins  or  oils  in  a  limited  supply  of  air.  The  lampblack 
is  collected  on  suitable  condensers.  Charcoal  is  made  by 
burning  wood  in  a  limited  supply  of  air  in  coal  kilns,  or 
by  distilling  wood  in  large  closed  retorts.  When  distil- 

65 


66  CARBON. 

lation  is  used,  valuable  products,  such  as  tar  and  acetic 
acid,  are  obtained  by  condensing  the  vapors. 

EXP.  54.  Color  about  50CC  of  water  with  any  organic  color, 
such  as  cochineal  or  litmus  solution.  Place  in  a  generating- 
flask  some  freshly  burned  charcoal  which  has  been  finely  pul- 
verized, or,  better,  some  good  boneblack,  and  then  add  about 
half  of  the  colored  solution.  Shake  the  contents  of  the  flask 
for  some  time,  and  then  filter.  Compare  the  color  of  the  fil- 
trate with  that  of  the  solution  which  was  not  treated.  What 
change  do  you  notice  ? 


FIG.  18. 

Charcoal  is  very  porous,  and  it  has  a  wonderful  power  of 
absorbing  gases.  Its  pores  therefore  contain  much  atmos- 
pheric oxygen.  Now  when  certain  vegetable  or  animal 
substances  are  brought  in  contact  with  this  oxygen,  they 
are  oxidized  and  thus  destroyed.  This  property  of  char- 
coal is  largely  utilized  in  refining  sugar,  in  making  water- 
filters,  and  for  disinfecting  purposes.  Charcoal  made  from 
blood  is  best  for  these  uses,  but  sugar-refiners  mostly  use 
Boneblack,  which  is  made  by  charring  bones.  Charcoal 
from  wood  is  principally  used  in  water-filters.  Wood 
charcoal  is  prepared  by  burning  wood  in  charcoal  kilns 
(Fig.  18). 


CARBON.  67 

Ex.  Why  should  a  water- filter  be  cleaned  and  renewed  frequently,  and 
why  often  allowed  to  run  dry  ?  How  can  you  obtain  carbon  from  kero- 
sene oil  ?  From  illuminating-gas  ?  What  makes  a  lamp  smoke  ?  For 
what  purposes  is  charcoal  used  in  the  arts  ? 

Stone  Coal  is  the  remains  of  a  magnificent  vegetation 
which  flourished  during  the  carboniferous  age  and  some 
of  the  periods  following.  Heat  and  pressure  are  the  prob- 
able agents  which  converted  this  vegetation  into  stone 
coal.  When  the  heat  and  pressure  were  great,  Anthracite, 
or  "  hard  "  coal,  was  produced ;  and  when  these  agencies 
were  less  intense,  Bituminous,  or  "  soft "  coal,  was  formed. 

Lignite  is  a  soft  coal  of  more  recent  origin,  being  derived 
from  deciduous  trees  similar  to  those  now  living. 

Peat  and  Turf  consist  largely  of  the  roots  and  stems  of 
low-growing  herbs  such  as  grasses  and  weeds. 

Ex.  For  what  purposes  are  the  different  kinds  of  coal  employed  ? 
Where  is  peat  largely  used  ? 

Grraphite,  also  known  as  "plumbago"  and  "black  lead," 
has  been  artificially  produced  in  insignificant  quantities  in 
iron  furnaces.  But  it  occurs  native  quite  plentifully  in 
many  localities.  It  is  largely  used  for  making  lead-pencils 
and  crucibles.  For  these  purposes  it  is  mixed  with  clay. 
Graphite  is  also  used  for  polishing  purposes,  in  coating 
powder  and  shot,  in  electrotyping,  and  in  the  manufacture 
of  stove-blacking. 

G-as  Carbon  is  found  in  the  retorts  used  for  distilling 
coal  in  the  manufacture  of  illuminating-gas.  This  form  of 
carbon  is  much  employed  in  making  plates  for  galvanic- 
batteries  and  for  making  carbon  pencils  for  electric  lamps. 

Diamonds  are  found  in  Africa,  India,  South  America, 
and  in  some  of  the  United  States.  They  occur  in  earthy 
detritus  or  in  clayey  shales :  the  method  of  their  formation 
is  not  understood. 


68  CAEBON. 

The  primary  form  of  the  diamond  crystal  is  octahedral 
(Fig.  19),  but  it  occurs  also  in  many  other  forms  derived 
from  this  primary  form. 

Diamonds  vary  in  color  from  the  pure,  limpid  variety  to 
the  black  diamond,  or  Carbonado.  The  colorless  diamond 
is  highly  prized  as  a  jewel,  while  the  yellowish  variety  is 
less  esteemed.  Blue  and  green  diamonds  are  beautiful 
and  rare,  and  consequently  high  in  price. 

The  diamond  is  insoluble  in  acids  and  in  alkalies;  it 
refracts  light  strongly,  whence  arises  its  brilliancy;  it  is 


FIG.  19.  —  Crystals  of  Diamond. 

the  hardest  substance  known  and  does  not  tarnish  under 
any  circumstances,  and  it  is  to  these  properties  that  it 
owes  its  value  as  a  jewel. 

At  high  temperatures  the  diamond  will  burn  in  an 
atmosphere  of  oxygen,  forming  carbon  dioxide,  CO2,  and 
leaving  a  small  amount  of  ash ;  in  fact,  it  is  almost  pure 
carbon. 

Low-grade  diamonds  are  used  for  cutting  glass  and  for 
writing  on  glass.  Diamond  dust  is  used  in  polishing  hard 
and  refractory  substances,  including  the  rough  diamond 
itself.  Black  diamonds  are  extensively  used  for  drill- 
points.  Equipped  with  these  drills,  the  miner  bores 


CARBON.  69 

through  the  hardest  rock  with  ease ;  and  thus  he  is  enabled 
to  explore  the  earth  to  a  depth  of  thousands  of  feet  while 
searching  for  its  hidden  treasure. 

EXP.  55.  Heat  a  few  grains  of  sugar  in  an  iron  spoon  or 
on  a  bit  of  porcelain.  Do  you  obtain  carbon  ?  Thus  try  starch, 
beeswax,  paraffin,  tallow,  and  gum  arabic.  If  the  substance 
burns  with  a  flame,  hold  a  cold  piece  of  metal  or  glass  in  the 
flame.  Are  all  these  carbon  compounds  ? 

In  this  way  it  may  be  shown  that  all  substances  of  veg- 
etable and  animal  origin  are  compounds  of  carbon.  In 
short,  so  great  is  the  number  of  these  compounds  that  they 
are  usually  treated  under  a  separate  heading  or  in  a  book 
devoted  exclusively  to  them.  This  branch  of  Chemistry 
is  called  The  Chemistry  of  the  Carbon  Compounds,  or 
Organic  Chemistry. 

77.  Tests  for  Carbon.  —  Free  carbon  is  readily  recognized 
in  any  of  its  forms  by  its  physical  properties. 

CARBON   AND   HYDROGEN. 

78.  Carbon  and  hydrogen  unite  to  form  a  multitude  of 
compounds.     In  this  chapter  we  shall  note  but  three  of 
these  compounds,  reserving  further  notice  to  a  succeeding 
chapter.     The  names  and  formulae  of  the  three  to  be  con- 
sidered here  are :  — 

Methane,  or  marsh  gas  ....  CH4. 
Ethylene,  or  olefiant  gas  .  .  .  C2H4. 
Acetylene C2H2. 

METHANE,  CH4. 

79.  Preparation  and  Properties.  —  EXP.  55.     Mix  2g  sodium 
acetate,  NaC2H302,  which  has  been  thoroughly  dried,  with  8g 


70 


CARBON  AND  HYDROGEN. 


sodium  hydroxide,  NaOH,  and  2g  finely  powdered  quicklime, 
CaO.  Fit  a  jet  delivery-tube  to  a  hard  glass  test-tube ;  place 
the  mixture  in  the  test-tube,  and  heat  the  contents  in  the 
Bunsen  flame.  When  the  gas  issues  freely,  hold  moistened 
strips  of  red  and  blue  litmus  paper  in  it,  and  finally  ignite  it. 
The  reaction  is 

NaC2H302  +  NaOH  =  ]STa2C03  +  CH4. 

Ex.  Is  methane  an  acid  ?  An  alkali  ?  Is  it  inflammable  ?  Deliver 
a  small  quantity  of  the  gas  in  a  large  test-tube,  and  mix  it  thoroughly 
with  air ;  apply  a  match  to  the  mouth  of  the  tube.  Is  methane  explosive  ? 

Methane  occurs  in  nature  very  plentifully,  especially  in 
connection  with  coal  and  in  the  oil  regions.     Natural  G-as, 
which   has   lately  risen  to   such  a  degree   of   usefulness, 
consists  largely  of  methane.     In  coal  mines  it  forms  the 
miner's  dreaded   "fire  damp,"   which  is  respon- 
sible  for  the    numerous    mine    explosions    that 
frequently  occur. 

Methane  also  occurs  in  marshy  places  and  in 
stagnant  pools,  being  produced  by  the  decay  of 
organic  substances.  From  this  fact  it  derived 
the  name  Marsh  Gas. 

Methane  is  neither  an  acid  nor  an  alkali ;  but 
as  we  shall  see  further  on,  it  is  important,  in 
that  it  is  the  lowest  member  of  a  series  of  hydro- 
carbon compounds,  many  of  which  are  of  the 
greatest  utility. 

Methane  is  not  readily  acted  on  by  reagents  > 
hence  it  affords  no  common  test  other  than  the  color  of 
its  bluish  yellow,  non-luminous  flame,  taken  together  with 
its  explosive  properties. 


FIG.  20. 


Ex.     Write  a  short  sketch  of  Sir  Humphry  Davy,  who  invented  the 
miner's  safety-lamp  (Fig.  20.) 


CARBON   AND   HYDROGEN.  71 

ETHYLENE,  OR  OLEFIANT  GAS,  C2H4. 

80.  Ethylene  is  formed  by  the  destructive  distillation  of 
coal ;  consequently  it  always  forms  a  valuable  constituent 
of  coal  gas. 

EXP.  56.  Place  10g  ethyl  alcohol,  C2H60,  in  a  generating- 
flask  which  has  been  provided  with  a  jet  delivery-tube ;  add 
50g  sulphuric  acid ;  heat  gently,  and  note  the  gas  which  escapes. 
Finally  ignite  the  jet,  and  note  the  flame,  which  is  the  same 
as  the  ordinary  luminous  gas-flame.  The  sulphuric  acid  simply 
deprives  the  alcohol  of  one  molecule  of  water :  — 

C2H«O  -  H20  =  Oft. 

EXP.  57.  Nearly  fill  the  bowl  of  a  common  clay  pipe  with 
powdered  bituminous  coal,  and  then  close  the  mouth  of  the 
bowl  by  a  covering  of  wet  clay.  Now  dry  the  clay,  and  heat 
the  bowl  of  the  pipe  in  the  Bunsen  flame,  and  ignite  the  gas 
escaping  from  the  stem  of  the  pipe.  It  is  Illuminating-Gas. 
When  the  gas  is  all  driven  out,  examine  the  contents  of  the 
bowl.  Coke  remains. 

Illuminating-gas  is  a  mixture  of  hydrogen,  methane, 
ethylene,  carbon  monoxide,  CO,  and  small  quantities  of 
various  other  gases.  One  of  the  by-products  formed  in 
distilling  coal  is  Coal  Tar.  From  this  remarkable  sub- 
stance many  useful  products  have  been  obtained,  among 
which  are  many  beautiful  dyes. 

81.  Test  for  Ethylene.  —  If   through   a  jar  of   ethylene 
chlorine    gas   be    passed,    a   heavy   oily   liquid,    ethylene 
chloride,   C2H4C12,  often   called  "Dutch   liquid,"  will  be 
formed ;    the    odor   of   this   substance    resembles   that   of 
chloroform. 


72  CARBON   AND   OXYGEN. 

ACETYLENE,  C2H2. 

82.  Acetylene  is  also  a  gas  possessing  a  disagreeable 
odor.      It   is  formed   when    an    ordinary    Bunsen   burner 
strikes  back  and  burns  at  the  base.     This  gas  is  remarka- 
ble, since  it  is  the  only  compound  of  hydrogen  and  carbon 
that  has  been  prepared  by  the  direct  union  of  these  ele- 
ments.    The  method  of  its  synthesis  is  extremely  simple : 
powerful  electric  sparks  are  passed  between  carbon  termi- 
nals in  an  atmosphere  of  hydrogen.    The  odor  of  acetylene 
betrays  its  presence. 

CARBON   AND    OXYGEN. 

83.  Two  oxides  of  carbon  are  known :  — 

Carbon  Monoxide,  CO ; 
Carbon  Dioxide,  C02. 

Of  these  gases,  the  latter  is  the  most  important.  The 
monoxide  is  formed  when  carbon  is  burned  in  a  limited 
supply  of  air :  -  C  +  0  =  CO. 

This  is  an  inflammable,  poisonous  gas  burning  with  a  blu- 
ish flame,  as  seen  in  the  flickering  flames  above  the  burning 
coal  in  coal  stoves  and  grates.  When  carbon  monoxide 
burns,  it  is  oxidized  to  the  dioxide  thus :  — 

CO  +  0  =  C02. 

CARBON  DIOXIDE,  CO2. 

84.  Occurrence.  —  This  important  gas,  often  called  car- 
bonic   acid   gas,    occurs    very   plentifully   in   nature.      It 
occurs  free  in  the  atmosphere  in  small  but  almost  unvary- 
ing proportions,  and  it  is  from  this  source  that  plants  ob- 
tain nearly  all  their  supply  of  carbon.     Limestone,  CaCO3, 


CABBON   AND   OXYGEN.  73 

and  other  mineral  carbonates  form  a  large  proportion  of 
the  earth's  crust.  Shells  and  many  coral  formations  are 
almost  pure  limestone. 

85.  Preparation  and  Properties. — EXP.  58.  Place  a  small 
quantity  of  calcium  hydroxide  solution  in  a  small  beaker. 
Using  a  glass  tube,  force  the  breath  through  this  solution. 
Note  the  white  precipitate  formed :  — 

Ca(OH)2  +  C02  =  CaC03  +  H20. 

The  carbon  dioxide  comes  from  the  breath.  Continue  to  pass 
the  breath  through  the  solution,  and  the  precipitate  dissolves. 

Carbon  dioxide  is  one  of  the  waste  products  of  the  body. 
Every  air-breathing  animal  exhales  this  gas  at  every 
breath. 

EXP.  59.  Place  a  burning  taper  in  a  wide-mouthed  bottle, 
and  cork  the  bottle  loosely.  When  the  taper  is  extinguished, 
remove  it,  and  pour  into  the  bottle  a  little  calcium  hydroxide 
solution.  Shake  thoroughly.  Do  you  obtain  a  white  precipi- 
tate ?  Is  carbon  dioxide  present  ?  Whence  came  it  ?  What 
equation  applies  ? 

Every  carbon-bearing  compound  when  burned  in  the  air 
produces  carbon  dioxide.  Volcanoes  also  send  out  large 
volumes  of  this  gas. 

EXP.  60.  Make  a  dilute  solution  of  sugar,  and  add  a  little 
baker's  yeast.  Fill  a  test-tube  with  this  solution ;  also  place 
a  small  quantity  of  the  same  in  an  evaporating-dish.  Invert 
the  test-tube,  and  place  its  mouth  below  the  solution  in  the 
dish,  and  allow  the  whole  to  stand  in  a  warm  place.  Fermen- 
tation soon  sets  in ;  bubbles  of  gas  rise  and  fill  the  tube.  Turn 
this  gas  out  into  a  clean  test-tube,  pouring  the  gas  as  if  it  were 
a  liquid,  and  then  test  the  contents  of  the  second  tube  for 
carbon  dioxide. 


74  CARBON    AND    OXYGEN. 

During  fermentation  and  in  the  natural  decomposition 
of  all  organic  substances,  carbon  dioxide  is  liberated.  The 
atmosphere  contains  by  volume  from  2.7  to  3.5  parts  of 
carbon  dioxide  in  10,000. 

Ex.  In  what  ways  is  carbon  dioxide  liberated  in  a  living-room  ?  In 
the  atmosphere  ?  Water  containing  carbon  dioxide  in  solution  can  dis- 
solve limestone ;  explain  the  disappearance  of  the  precipitate  formed  in 
Exp.  58. 

EXP.  61.  Place  about  10g  of  coarsely  pulverized  limestone 
or  marble,  CaC03,  in  a  generating-flask,  fitted  with  a  V-shaped 
delivery-tube.  Cover  the  limestone  with  dilute  hydrochloric 
acid,  and  warm  gently  if  necessary.  The  following  reaction 

occurs :  — 

CaC03  +  2  HC1  =  CaCl2  +  H20  +  C02. 

The  gas  may  be  collected  by  delivering  it  at  the  bottom  of  any 
deep  and  narrow  vessel,  or  it  may  be  stored  in  gas-bags. 

EXP.  62.  Fill  a  wide  test-tube  with  carbon  dioxide,  and 
then  lower  into  it  a  burning  taper.  What  occurs  ? 

EXP.  63.  Place  a  mouse  in  a  jar  of  carbon  dioxide.  Note 
the  rapidly  fatal  effects  of  the  gas. 

EXP.  64.  Attach  a  common  clay  pipe  to  the  uozzle  of  a 
gas-bag  filled  with  carbon  dioxide.  Dip  the  bowl  of  the  pipe 
in  a  soap-bubble  solution,  and  allow  the  gas  to  escape,  forming 
a  bubble.  Shake  the  bubble  loose.  Does  it  rise  or  fall  ?  Is 
carbon  dioxide  heavier  or  lighter  than  air  ? 

EXP.  65.  Place  the  tip  of  the  delivery-tube  into  the  bottom 
of  a  test-tube  filled  with  cold  water.  Allow  the  gas  to  bubble 
up  through  the  water  for  some  time.  Test  the  water  as  fol- 
lows :  (1)  Taste  it.  Is  it  acid  ?  Also  test  it  with  blue  litmus 
paper.  (2)  To  a  portion  of  the  water  add  calcium  hydrox- 
ide solution.  Did  the  water  dissolve  any  carbon  dioxide? 
(3)  Boil  the  remainder  of  the  water,  and  test  as  before.  What 
effect  does  boiling  have  upon  solutions  of  carbon  dioxide  in 
water  ? 


CARBON   AND    OXYGEN.  75 

When  large  supplies  of  carbon  dioxide  are  required, 
they  are  obtained  by  acting  on  some  of  the  metallic  carbon- 
ates by  means  of  an  acid.  Thus  soda-water  fountains  are 
charged  by  treating  powdered  marble  with  sulphuric  acid. 
In  baking-powders  carbon  dioxide  is  liberated  by  the  reac- 
tion between  sodium  carbonate  and  cream  of  tartar,  or  acid 
potassium  tartrate,  KHC4H4O6.  Sometimes  alum  is  inju- 
riously employed  instead  of  the  cream  of  tartar. 

Carbon  dioxide  is  heavier  than  air,  having  a  specific 
gravity  of  1.529,  while  one  litre  weighs  1.965g.  In  conse- 
quence of  its  high  specific  gravity,  it  collects  in  wells, 
caves,  and  mines ,  and  many  persons  lose  their  lives  by 
going  down  into  places  filled  with  this  gas.  It  seems  to 
produce  its  fatal  effects  by  suffocation. 

Carbon  dioxide  is  a  very  stable  compound,  but  its  separa- 
tion can  be  effected  by  the  method  shown  in  -the  following 
experiment :  — 

EXP.  66.  Hold  a  piece  of  burning  magnesium  ribbon  in  a 
jar  of  carbon  dioxide.  Is  carbon  liberated? 

Since  we  have  a  series  of  salts,  the  carbonates,  the  exist- 
ence of  a  corresponding  acid  would  be  suggested.  Thus 
if  we  regard  carbon  dioxide  as  the  anhydride  of  that  acid, 
we  have :  —  C02  +  H20  =  H2C03. 

And  we  might  suppose  that  the  metals  unite  with  this  acid 
to  form  the  carbonates.  Again,  a  solution  of  carbon  diox- 
ide in  water  has  a  weak  acid  reaction  to  test  paper.  But 
notwithstanding  all  these  facts,  carbonic  acid  has  not  been 
prepared  in  a  pure,  concentrated  state. 

86.   Tests  for  Carbon  Dioxide  and  the  Carbonates, —1.  If 

the  free  gas  he  led  through  a  solution  of  calcium  hydroxide, 
Ca(OH)2,  a  white  precipitate  of  calcium  carbonate  is  formed. 


76  CARBON   AND   OXYGEN. 

2.  If  the  free  gas  be  in  a  water  solution,  it  may  be  placed 
in  a  geiieratiiig-flask  fitted  with  a  delivery-tube,  and  boiled 
out  and  passed  through  calcium  hydroxide  as  before. 

3.  Any  of  the  mineral  carbonates  will  effervesce  with 
hydrochloric  acid,  yielding' free  carbon  dioxide  which  may 
be  generated  in  a  flask  and  tested  as  in  1. 

CYANOGEN,  CN  OR  Cy. 

87,  But  one  compound  of  carbon  and  nitrogen  has  been 
prepared,  and  that  is  the  gas,  Cyanogen.     When  mercuric 
cyanide,  Hg(CN)2,  is  heated,  cyanogen  is  liberated;   but 
the  gas  is  too  poisonous  for  the  beginner  to  prepare. 

HYDROCYANIC  OR  PRUSSIC  ACID,  HCN. 

88.  Prussic  acid  is  one  of  the  most  deadly  poisons  known. 
It  occurs  in  minute  quantities.    It  can  be  prepared  by  treat- 
ing mercuric  cyanide,  Hg(CN)2  with  hydrogen  sulphide, 
H2S,  thus  :  — 

Hg(CN)2  +  H2S  =  HgS  +  2  HCN. 

The  acid  has  a  faint  and  peculiar  odor  resembling  peach 
blossoms.     The  beginner  may  omit  its  preparation. 

An  important  class  of  compounds  may  be  regarded  as 
derived  from  this  acid.  These  are  the  cyanides,  among 
which  is  the  well-known  potassium  cyanide,  KCN,  which 
is  used  in  silver  electroplating  and  as  an  insecticide. 

89  Test  for  the  Cyanides.  —  The  cyanides  always  emit  a 
peculiar  odor  resembling  that  of  the  acid.  But  in  case  of 
doubt  a  good  test  follows :  Add  to  the  solution  potassium 
hydroxide,  KOH,  and  then  add  ferrous  sulphate,  FeSO4. 
Now  shake  thoroughly  and  acidulate  the  contents  of  the 
tube  with  hydrochloric  acid.  If  a  cyanide  be  present,  a 
deep  blue  precipitate  (Prussian  blue)  will  be  formed. 


EXERCIS 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  Test  as  many  different  kinds  of  shells  as  you  can  find  for  carbonates. 
Also  test  several  specimens  of  rocks  for  carbonates.    Usually  it  will  be 
sufficient  to  add  hydrochloric  acid,  HC1,  and  note  the  effervescence,  with- 
out passing  the  gas  through  lime-water. 

2.  Read  in  some  text  on  Geology  a  description  of  the  carboniferous 
age. 

3.  Read  all  the  authorities  at  hand  on  the  topic  of  ventilation. 

4.  Procure  a  stoppered  bell- jar,  or  a  large  bottle  from  which  the  bottom 
has  been  evenly  cut  off  and  ground  so  that  it  will  set  on  a  board  or  on  the 
desk  nearly  air-tight.    Let  this  represent  a  school- room.    Now  let  a  lighted 
taper  represent  the  pupils  sitting  hi  the  room.     Make  the  following  exper- 
iments, and  show  what  principles  they  illustrate  in  ventilation  :  — 

(a)  Place  the  bell-jar  on  the  desk,  and  insert  the  stopper.  This  now 
represents  a  room  with  no  ventilation.  Remove  the  stopper,  insert  the 
lighted  taper,  and  then  return  the  stopper.  You  now  have  a  representa- 
tion of  a  room  with  no  ventilation,  and  with  the  pupils  sitting  in  it.  What 
occurs  ?  What  lesson  does  this  teach  ? 

(6)  Most  country  school-houses  have  a  hole  in  the  ceiling  for  a  venti- 
lator. The  jar  sitting  on  the  desk,  with  the  stopper  removed,  will  repre- 
sent such  a  room.  Let  the  air  in  the  jar  be  pure,  and  insert  the  burning 
taper,  leaving  out  the  stopper.  This  arrangement  represents  such  a  room 
with  the  pupils  sitting  in  it.  What  occurs,  and  what  lesson  is  taught  ? 

(c)  Now  put  the  stopper  hi  place,  and  let  one  edge  of  the  jar  project 
slightly  over  the  edge  of  the  desk.    This  represents  a  room  with  a  venti- 
lating opening  at  the  bottom.     Insert  the  burning  taper  when  the  jar  is  so 
placed.     What  occurs,  and  what  is  the  deduction  therefrom  ? 

(d)  Now  leave  the  stopper  out,  and  let  the  edge  of  the  jar  project  as 
before.     We  now  have  two  openings  for  ventilation.     Insert  the  lighted 
taper,  and  note  the  results.    WTiat  is  the  course  taken  by  the  air  ?    What 
is  the  course  of  the  circulation  in  the  other  arrangements  ?     What  lesson 
have  you  learned  ? 

5.  What  weight  of  CO2  can  you  obtain  from  100*  of  CaCO3  ?     How 
many  litres  would  this  be  under  standard  conditions?     At  14°  C.  and 
758mm,  how  many  litres  ? 

6.  How  could  you  test  a  well  for  CO2  ?    If  one  man  loses  his  life  in  a 
well  containing  choke  damp,  why  does  another  person  almost  invariably 
lose  his  life  in  the  same  well  also  ?    What  ought  always  to  be  done  before 
venturing  into  a  well  ? 


78 


EXERCISES. 


7.  Hold  a  piece  of  fine  wire  gauze  down  over  the  Bunseii  flame,  Fig.  22. 
Explain  what  takes  place. 

8.  Explain  the  action  of  the  miner's  safety-lamp,  Fig.  20. 

9.  Generate  some  sulphuretted  hydrogen  (Art,  95),  and  pass  the  gas 
;hrough  a  test-tube  of  cold  water.     Place  the  solution  thus  formed  in  a 


FIG.  21. 


FIG.  22. 


flask.     Add  some  powdered  charcoal,  and  shake.     Has  the  odor  disap- 
peared ?     Explain. 

10.  What  substances  are  produced  during  the  combustion  of  hydro- 
carbon compounds  ? 

11.  Fill  a  tumbler  or  beaker-glass  with  carbon  dioxide,  and  then  pour 
the  gas  into  a  similar  vessel  containing  a  lighted  taper  (Fig.  21).     Explain 
what  occurs. 


CHAPTER   VII. 

SULPHUR,    SELENIUM,   AND   TELLURIUM,    AND 
THEIR    COMPOUNDS. 

SULPHUR. 

DATA   FOR   COMPUTATIONS.  —  Symbol,  S  ;   Atomic  Weight,  32  ;    Specific 
Gravity  (crystals),  2.05;  Melting- Point,  115°  O.;  Boiling-Poiut,  447°  C. 

90.  Occurrence.  —  Sulphur    occurs    native    in    volcanic 
regions.     Its  compounds  are  also  widely  distributed.     Iron 
pyrites,  FeS2,  or  fool's  gold  ;  galena,  PbS  ;  cinnabar,  HgS  ; 
gypsum,  CaSO4  -f  2  H2O,  and  heavy  spar,  BaSO4,  are  among 
the  most  plentiful  compounds. 

91.  Preparation  and  Properties. — Native  sulphur  is  read- 
ily separated  from  its  impurities  by  fusion.    It  is  afterward 
distilled,  and  the  vapors  are  conducted  into  suitable  con- 
densing chambers.     If  the  chamber  be  cold,  flowers  of  sul- 
phur are  obtained.     If  the  temperature  of  the  chamber  is 
at  about  the  melting-point  of  sulphur,  it  is  obtained  as  a 
liquid  which  is  drawn  off  and  cast  into  sticks  known  as 
roll  sulphur  or  brimstone.     But  the  greater  part  of  the  sul- 
phur used  in  the  arts  is  simply  the  crude  product  obtained 
by  fusion. 

EXP.  67.  Dissolve  1«  slaked  lime  in  13™  of  water.  Add 
2g  flowers  of  sulphur,  and  boil.  Now  filter  the  solution,  and 
acidify  with  hydrochloric  acid.  A  white  precipitate  of  finely 
divided  sulphur  is  obtained.  At  first  calcium  pentasulphide, 

79 


80  SULPHUR. 

CaS5,  is  obtained ;  "this  is  decomposed  by  the  acid  which  is 
finally  added.     Write  the  equation. 

The  product  obtained  in  the  preceding  experiment  is  the 
lac  sulphuris,  or  milk  of  sulphur,  of  the  Pharmacopoeia.  It 
is  used  in  medicine. 

EXP.  68.  Place  a  small  quantity  of  flowers  of  sulphur  in 
a  test-tube,  and  add  carbon  disulphide,  CS2;  close  the  tube 
with  the  thumb,  and  shake  till  the  sulphur  is  dissolved^  Now 
pour  the  solution  into  a  small  beaker,  and  allow  it  to  evaporate 
in  the  air  without  heat.  Note  the  sulphur  crystals  obtained. 


FIG.  23. 

The  primary  form  of  the  sulphur  crystal  is  the  octahe- 
dron (Fig.  23).  But  in  all  there  are  no  less  than  thirty 
different  forms  derived  from  the  primary  crystal. 

EXP.  69.  Melt  sulphur  in  a  test-tube,  and  then  heat  until 
it  becomes  black  and  fluid.  Now  turn  the  molten  mass  into 
cold  water  (Fig.  24).  Examine  the  product. 

This  experiment  furnishes  plastic  sulphur,  which 
strongly  resembles  caoutchouc.  When  rubber  gum  is 
heated  with  sulphur  at  moderate  temperatures,  a  better 
material  for  some  purposes  is  obtained  than  the  pure  gum 


SULPHITE   AND   HYDKOGEN.  81 

itself.  When  higher  temperatures  are  employed,  vulcanite 
or  ebonite  is  obtained.  Large  quantities  of  sulphur  are 
thus  consumed. 

EXP.  70.  Heat  a  pine  splinter,  and  dip  it  in  flowers  of 
sulphur.  Now  ignite,  and  note  the  fumes,  S02. 

Sulphur  is  largely  employed  in  making  matches,  in 
bleaching  straw  goods  and  hops,  in  preparing  sulphuric 
acid,  and  in  the  manufacture  of  gun-powder. 

92.  Tests  for  Free  Sulphur.  —  Free  sulphur  can  be  recog- 
nized by  its  physical  properties  and  by  its  fumes  when 
ignited. 

SULPHUR   AND   HYDROGEN. 

93.  Sulphur  and  hydrogen  form  two  compounds :  — 

Hydrogen  sulphide,  H2S. 
Hydrogen  persulphide,  H2S2(?). 

Of  these  compounds,  the  first  is  the  more  important.  The 
second  has  no  industrial  use. 

HYDROGEN  SULPHIDE,  H^. 

94.  Occurrence.  —  This    substance    is    a    gas   commonly 
called  Sulphuretted  Hydrogen.     It  occurs  in  large  quanti- 
ties, both  free  and  combined.     It  is  sulphuretted  hydrogen 
that  gives  the  offensive  odor  to  many  "  sulphur  springs  " 
and  mineral  waters  ;  it  is  a  product  of  volcanic  action,  and 
of  the  decomposition  of  albuminous  substances,  as  noticed 
in  the  odor  of  rotten  eggs.     It  is  produced  periodically  in 
some  surface  wells  by  the  action  of  organic  substances,  such 
as  wooden  curbing  and  wooden  pumps,  on  iron  pyrites 
in  the  presence  of  mineral  ingredients  dissolved  in  the 
waters  of  the  wells. 


82  STTLPHTJK   AND   OXYGEN. 

95.  Preparation  and  Properties.  —  EXP.  71.     Place  two  or 
three  small  pieces  of  ferrous  sulphide,  FeS,  in  a  generating- 
flask  fitted  with  a  V-shaped  delivery-tube.     Cover  the  lumps 
with  water,  and   then  add   a   few  drops   of   sulphuric   acid. 
Insert  the  delivery-tube,  and  the  apparatus  is  now  ready  for 
use.     The  reaction  is  :  — 

FeS  +  H2S04  =  FeS04  +  H2S. 

Note  the  odor  of  the  gas,  and  finally  ignite  it.  Extinguish  the 
flame,  and  allow  the  gas  to  bubble  up  through  a  solution  of 
copper  sulphate,  CuS04,  in  a  test-tube.  Note  the  precipitate 
formed.  Thus  pass  the  gas  through  a  solution  of  lead  acetate, 
Pb(C2H302)2. 

Hydrogen  sulphide  forms  a  series  of  salts,  the  sulphides. 
As  in  the  case  of  hydrochloric  acid,  this  acid  is  also  much 
used  in  analytical  work  as  a  group  reagent.  In  such  work, 
it  is  prepared  precisely  as  in  the  preceding  experiment. 

96.  Tests   for   Hydrogen   Sulphide,   Free   or    Combined. — 
1.  The  free  gas  may  be  detected  by  its  odor  and  by  its 
blackening  a  strip  of  paper  moistened  with  lead  acetate, 

Pb(C2H302)2. 

2.  A  sulphide  is  tested  thus :  Pulverize  the  substance  to 
be  tested,  mix  it  with  sodium  carbonate,  Na2CO3,  on  a  bit 
of  porcelain  or  platinum  foil,  and  fuse  it  in  the  Bunsen 
flame.  Place  the  fused  mass  on  a  clean  silver  coin  and  add 
a  drop  of  water.  If  a  sulphide  be  present,  a  black  spot 
will  appear  on  the  silver. 

SULPHUR  AND   OXYGEN. 

97.  We  shall  notice  two  oxides  of  sulphur  :  — 

Sulphur  dioxide,  S02. 
Sulphur  trioxide,  S03. 


SULPHUR    AND    OXYGEN.  83 

Both  these  oxides  are  important  from  a  chemical  point  of 
view,  since  they  are  respectively  the  anhydrides  of  sulphu- 
rous acid,  H2SO3,  and  sulphuric  acid,  H2SO4.  They  unite 
with  water  thus  :  — 

SO2  +  H20  =  H2SO3;   and  SO3  +  H2O  =  H£O<. 

The  trioxide  is  prepared  by  passing  a  mixed  stream  of  sul- 
phur dioxide  and  oxygen  over  finely  divided  platinum  in 
a  highly  heated  porcelain  tube.  The  dioxide  deserves  a 
more  extended  notice. 

SULPHUR  DIOXIDE,  SO2. 

98.  Preparation  and  Properties.  —  EXP.  72.  Place  a  small 
quantity  of  powdered  galena,  PbS,  in  a  hard  glass  tube  open 
at  both  ends,  and  heat  strongly  in  the  Bunsen  flame.  Note 
the  gas  escaping  from  the  tube. 

EXP.  73.  Place  some  fine  copper  filings  in  a  test-tube,  and 
cover  with  strong  sulphuric  acid.  Heat  gently,  and  note  the 
escaping  gas.  Hold  a  piece  of  moist  wheat  straw  in  the  vapors. 
Also  try  the  effect  upon  bits  of  unbleached  silk  or  woollen  yarn. 
What  occurs  ?  The  copper  and  acid  react  thus  :  — 
Cu  +  2  H2S04  =  CuS04  +  2  H20  +  SO* 

Sulphur  dioxide  occurs  free  in  volcanic  gases.  It  finds 
many  useful  applications  in  the  arts,  and  is  manufactured 
in  enormous  quantities.  For  bleaching  purposes  it  is  pre- 
pared by  burning  sulphur  in  the  air.  In  sulphuric  acid 
manufacture  it  is  prepared  in  the  same  way,  and  also  by 
roasting  iron  pyrites  or  some  other  sulphide.  Of  late  this 
gas  is  used  in  manufacturing  paper  from  wood  by  the  sul- 
phite process.  For  this  purpose,  the  gas  is  run  into  tanks 
of  lime-water  or  calcium  hydroxide  solution.  The  liquor 
thus  prepared  is  used  for  reducing  the  chipped  wood  to 
paper  pulp. 


84  THE   SULPHUR   OX  ACIDS. 

99,  Test  for  Sulphur  Dioxide.  —  Free  sulphur  dioxide  may 
be  recognized  by  its  odor,  which  is  well  known,  resembling 
that  of  burning  matches. 


THE   SULPHUR   OXACID3. 

100,  There  are  eight  acids  in  this  series,  as  shown  in  the 
following  list :  — 

Hyposulphurous  acid  ....  H2S02. 

Sulphurous  acid H2S03. 

Sulphuric  acid H2S04. 

Thiosulphuric  acid H2S203. 

Dithionic  acid H2S206. 

Trithionic  acid H2S306. 

Tetrathionic  acid H2S4O6. 

Pentathionic  acid H2S506. 

Of  these  acids,  but  three  are  of  importance  to  the  beginner, 
—  sulphurous,  sulphuric,  and  thiosulphuric  acids.  The 
last  has  not  been  prepared,  but  its  salts  are  used  for  some 
purposes,  as  in  photography.  Only  the  test  for  this  acid 
will  be  given. 

By  inspection  it  will  be  seen  that  in  this  series  of  acids 
each  contains  two  atoms  of  hydrogen.  One  or  both  of 
these  atoms  is  replaceable  by  a  metal ;  thus  each  of  these 
acids  may  give  rise  to  acid  or  normal  salts.  For  example, 
we  have  acid  or  monosodium  sulphate,  NaHSO4,  or  sodium 
sulphate,  Na2SO4. 

When  an  acid  has  one  replaceable  hydrogen  atom,  it  is 
called  a  monobasic  acid ;  when  it  has  two,  it  is  called  diba- 
sic, ;  three,  tribasic ;  and  with  four,  it  is  tetrabasic.  We 
have  had  examples  of  the  first  two;  and  illustrations  of 
the  others  will  appear  further  on. 


THE    SULPHUR   OXACIDS.  85 


SULPHUROUS  Aero, 

101.  Preparation  and  Properties.  —  EXP.  74.    Pass  sulphur 
dioxide  gas  (Exp.  73)  into  a  test-tube  of  cold  water.     Free 
sulphurous  acid  will  be  obtained.     Write  the  equation. 

EXP.  75.  Pass  sulphur  dioxide  gas  into  a  solution  of  potas- 
sium hydroxide,  KOH.  Potassium  sulphite  will  be  formed  :  — 

2  KOH  +  S02  =  K2S03  +  H20. 
Save  the  acid  and  the  salt  for  the  tests  in  the  next  article. 

Both  the  free  acid  and  its  salts  are  used  to  a  limited 
extent  in  commerce.  They  both  act  as  bleaching  reagents. 
On  standing,  they  absorb  oxygen,  passing  into  sulphuric 
compounds.  When  the  sulphites  are  treated  with  acids, 
sulphur  dioxide  is  liberated,  thus  :  — 

K2S03  +  2  HC1  =  2  KC1  +  H2O  +  S02. 

102.  Tests  for  Sulphurous  Acid  and  the  Sulphites.  —  1.  Free 
sulphurous  acid  may  be  detected  by  its  odor  of  burning 
matches. 

2.  A  sulphite  is  detected  by  adding  hydrochloric  acid  to 
its  solution.     The  solution  remains  clear  and  gives  off  the 
odor  of  the  free  acid. 

3.  A   sulphite   in  solution  yields  a  white   precipitate, 
BaSO3,  with  barium  chloride,  BaCl2.     This  precipitate  is 
soluble  in  hydrochloric  acid.     If  a  portion  of  the  barium 
precipitate  is  treated  with  nitric  acid,  the  insoluble  barium 
sulphate,  BaSO4,  is  obtained. 

SULPHURIC  ACID,  H^O^ 

103.  Occurrence.  —  Small  quantities  of  free  sulphuric  acid 
occur  in  some  volcanic  waters.     Its  compounds,  the  sul- 


86  THE   SULPHUR   OXACIDS. 

phates,  occur  plentifully  in  nature.  Thus  gypsum  or  land 
plaster,  CaSO4+  2  H2O,  occurs  in  vast  deposits. 

It  is  safe  to  say  that  this  is  the  most  important  acid 
known  to  chemistry  and  to  commerce.  Although  the 
student  has  this  acid  on  his  table  and  has  used  it  from 
the  very  beginning  of  his  work,  it  will  be  well,  in  view 
of  its  great  importance,  to  illustrate  the  method  of  its 
manufacture. 

104.  Preparation  and  Properties.  —  Sulphuric  acid  is  man- 
ufactured on  the  large  scale  by  oxidizing  sulphur  dioxide 
in  the  presence  of  moisture  thus  :  — 

S02  +  0  +  H20  =  H2S04. 

Oxygen  from  the  air  is  used  in  oxidizing  the  dioxide. 
But  sulphur  dioxide  cannot  take  up  atmospheric  oxygen 
directly.  There  is  a  substance,  however,  that  can  unite 
directly  with  the  oxygen  of  the  air,  and  that  is  nitrogen 
dioxide,  NO.  The  reaction  in  this  case  is 

NO  +  0  =  N02. 

Now  sulphur  dioxide  can  take  the  atom  of  oxygen  just 
taken  from  the  air  by  the  nitrogen  dioxide  thus  :  — 


It  will  be  noticed  that  the  NO2  has  gone  back  to  its  origi- 
nal form,  NO,  and  is  again  ready  to  take  another  atom  of 
oxygen  from  the  air,  after  which  it  will  be  able  to  oxidize 
another  molecule  of  SO2,  when  the  same  changes  will 
be  repeated  in  the  same  order  an  indefinite  number  of 
times. 

But  we  had  a  molecule  of   SO3.     This  unites  with  a 
molecule  of  water  thus  :  — 


THE    SULPHUR   OXACIDS. 


87 


And  so  we  have  a  molecule  of  sulphuric  acid,  and  the  his- 
tory of  this  one  molecule  is  the  history  of  all. 

Ex  P.  76.  Fig.  25  shows  an  apparatus  for  making  a  small 
quantity  of  sulphuric  acid.  B  is  a  generator  containing  copper 
filings  and  sulphuric  acid  to  generate  the  sulphur  dioxide.  D 
is  a  tube  leading  from  a  bellows  to  supply  the  necessary  air. 
C  is  a  flask  containing  water  to  furnish  steam.  A  contains 
copper  filings  and  nitric  acid  to  furnish  the  nitrogen  dioxide. 
E  is  an  escape-pipe  for  waste  gases.  G  is  a  globe  used  as  a 


FIG.  25. 


condensing-chamber.  A  clear  glass  carboy  or  large  bottle  will 
answer  as  well.  It  is  perhaps  needless  to  say  that  all  the 
gases  are  delivered  into  the  globe  simultaneously,  and  that 
farther  directions  for  manipulation  are  unnecessary. 

In  actual  practice  the  manufacturer  varies  the  details  of 
the  foregoing  description  but  slightly.  He  generates  the 
sulphur  dioxide  by  roasting  pyrites  or  by  burning  crude 
sulphur.  The  steam  is  generated  in  a  boiler,  and  lead-lined 


88  THE   SULPHUK    OXACIDS. 

chambers  are  used  for  condensing  purposes.  Sometimes 
nitric  acid  is  used  in  place  of  the  nitrogen  dioxide.  This 
acid  is  generated  from  sodium  nitrate  and  sulphuric  acid, 
as  previously  explained.  In  this  case  what  takes  place 
may  be  represented  by  the  following  equation  :  — 

2  HN03  +  3  S02  +  2  H20  =  3  H2S04  +  2  NO. 

Of  course  it  is  impossible  to  tell  precisely  what  the  exact 
changes  are,  or  in  what  order  they  occur,  but  as  to  the 
final  results  there  can  be  no  doubt.  It  will  be  noticed  that 
nitrogen  dioxide,  NO,  also  appears  when  the  nitric  acid  is 
used. 

The  acid  formed  in  the  leaden  chambers  is  weak,  having 
a  specific  gravity  of  1.55.  It  is  concentrated  in  leaden 
pans  until  it  reaches  a  specific  gravity  of  1.71,  when  it  is 
withdrawn  and  further  concentrated  and  purified  in  glass 
or  platinum  stills  until  its  specific  gravity  is  1.84,  when  it 
is  ready  for  the  market. 

EXP.  77.  Moisten  a  pine  splinter  with  strong  sulphuric  acid. 
What  occurs  ?  Thus  try  a  lump  of  sugar  and  a  grain  of  starch. 

Sulphuric  acid  chars  vegetable  substances.  It  abstracts 
water,  or  at  least  hydrogen  and  oxygen.  This  acid  eagerly 
absorbs  moisture,  and  thereby  becomes  dilute.  When  the 
union  is  taking  place,  much  heat  is  evolved ;  therefore  it 
should  be  an  unvarying  rule  when  diluting  sulphuric  acid 
to  add  the  acid  to  the  water,  and  not  the  water  to  the 
acid. 

.The  uses  of  sulphuric  acid  in  the  manufactures  are 
many  and  important.  Thus  it  is  used  in  bleaching  fac- 
tories, in  soda  factories,  in  paper  mills,  and  in  manufac- 
turing artificial  fertilizers  and  in  many  other  important 
operations. 


SULPHUR   AND  .CARBON.  89 

NORDHAUSEN  OR  FUMING   SULPHURIC    ACID,  HaSO^  SO3. 

105.  Fuming  sulphuric  acid  is  made  by  distilling  ferrous 
sulphate  containing  but  one  molecule  of  water :  — 

4  FeS04  +  H20  =  2  Fe2O3  +  2  S02  +  H2SO4,  SO3. 

This  acid  is  used  in  dissolving  indigo  in  the  process  of 
dyeing  Saxony  blue,  and  in  making  the  coal-tar  colors.  It 
is  converted  by  means  of  water  into  ordinary  sulphuric  acid 
with  the  evolution  of  much  heat. 

106.  Tests  for  Sulphuric  Acid  and  the  Sulphates.  —  1.  Free 
sulphuric  acid  or  a  soluble  sulphate  in  solution  is  tested 
by  adding  barium  chloride,  BaCL,  which  throws  down  the 
white  insoluble  precipitate,  barium  sulphate,  BaSO4.     Add 
hydrochloric  acid  to  test  the  solubility  of  the  precipitate. 

2.  An  insoluble  sulphate  is  fused  on  charcoal  with 
sodium  carbonate,  the  fused  mass  placed  on  a  silver  coin 
and  moistened :  a  black  spot  is  obtained.  Now  fuse  a 
fresh  portion  of  the  substance  with  sodium  carbonate  on 
porcelain,  place  on  silver  and  moisten:  no  black  spot  is 
obtained  if  the  substance  is  a  sulphate. 

107.  Tests  for  the  Thiosulphates.  —  If  not  in  solution,  dis- 
solve the  substance  in  water  and  add  hydrochloric  acid :  a 
white  precipitate  of  sulphur  is  obtained,  and  sulphur  diox- 
ide set  free  if  a  thiosulphate  be  present. 

SULPHUR   AND    CARBON. 

108.  Carbon  Bisulphide,  CS2,  is  the  only  known  compound 
of  sulphur  and  carbon.    It  is  prepared  by  passing  vaporized 
sulphur  over  charcoal  heated  to  redness  in  a  cylinder. 

This  substance  is  a  limpid  liquid  in  its  pure  form  and 


90 


SELENIUM   AND   TELLURIUM. 


possesses  a  pleasant  ethereal  odor.  But  in  an  impure  state 
it  is  colored  and  possesses  a  powerful,  sickening  odor.  Its 
fumes  are  poisonous  ;  hence  it  is  much  used  for  destroying 
vermin  and  as  an  insecticide.  In  optics  it  is  used  for  fill- 
ing prisms,  while  in  the  arts  it  is  used  as  a  solvent  for 
rubber  gum.  Its  use  in  the  laboratory  has  already  been 
exemplified. 

The  odor  of  the  disulphide  will  serve  as  a  test. 


SELENIUM   AND    TELLURIUM. 

109.  Selenium :  Symbol,  Se  ;  Atomic  Weight,  79 ;  Specific 
Gravity,  4.3.  —  Selenium  is  a  rare  element  closely  resem- 
bling sulphur.     Berzelius  discovered  it  in  1817  in  the  resi- 
due collected  from  the  sulphuric  acid  chambers  at  Gripsholm. 
In  a  finely  divided  state  and  viewed  by  transmitted  light, 
selenium  has  a  reddish  color.     It  exists  in  three  modifica- 
tions :  viz.  amorphous,  vitreous,  and  crystalline  selenium. 

110.  Tellurium:  Symbol,  Te ;  Atomic  Weight,  128 ;  Spe- 
cific Gravity,  6.24.  —  Tellurium  is  a  rare  element.     It  is 
a  brittle,  bluish  white  solid,  possessing  a  decided  metallic 
lustre.     In  its  chemical  compounds  it  resembles  selenium 
and  sulphur.     The  following  table,  given  simply  for  in- 
spection, will  reveal  how  closely  related  these  three  ele- 
ments are. 


ATOMIC 
WEIGHT. 

SPECIFIC 
GRAVITY. 

SOME  COMPOUNDS. 

Sulphur    .... 

32 

2.05 

H2S 

S02 

S03 

H2S04 

Selenium  .... 

79 

4.30 

H2Se 

SeO2 

Se03 

H2Se04 

Tellurium     .     .     . 

128 

6.24 

H2Te 

Te02 

TeO3 

H2Te04 

EXERCISES.  91 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  How  much  sulphur  would  be  required  to  produce  82  pounds  of 
sulphuric  acid  ? 

2.  Test  a  piece  of  vulcanized  rubber  for  sulphur  by  fusing  with  sodium 
carbonate,  etc. 

3.  Test  a  sample  of  drinking-water  for  a  sulphate. 

4.  Place  some  iron  filings  in  a  test-tube  ;  add  dilute  sulphuric  acid,  and 
heat  gently.     What  gas  is  given  off  ?     (Suo.  Test  with  a  match  flame.) 
Evaporate  the  contents  of  the  tube  to  dry  ness  in  an  evaporating- dish  after 
the  iron  has  dissolved,  and  test  the  residue  for  a  sulphate.     What  sub- 
stances were  obtained  ?     Write  the  equation. 

5.  How  can  you  distinguish  between  a  sulphite  and  a  thiosulphate  ? 

6.  What  impurities  would  one  expect  to  find  in  commercial  sulphuric 
acid,  when  the  material  employed  and  the  process  of  manufacture  are 
taken  into  consideration  ? 


CHAPTER   VIII. 

SILICON,    BORON,    AND    PHOSPHORUS,    AND   THEIR 
COMPOUNDS. 

DATA  FOR  COMPUTATIONS.  —  SILICON  :  Symbol,  Si ;  Atomic  Weight,  28  ; 
Specific  Gravity,  2.49.  — BORON:  Symbol,  B;  Atomic  Weight,  11; 
Specific  Gravity,  2.5.  —  PHOSPHORUS  :  Symbol,  P;  Atomic  Weight,  31  ; 
Specific  Gravity,  1.83. 

SILICON. 

111.  Occurrence,  etc.  —  Silicon  is  a  very  abundant  ele- 
ment, which,  however,  never  occurs  free.  It  forms  from 
22.8  to  36.2  per  cent  of  the  earth's  crust.  With  oxygen  it 
forms  the  abundant  compound,  silica,  SiO2.  Silica  is 
known  to  us  in  many  different  forms.  Thus  sand,  sand- 
stone, quartz,  quartzite,  agate,  opal,  chalcedony,  flint,  chert, 
and  hone-stone  are  almost  pure  silica.  They  owe  their  dif- 
ferent appearances  sometimes  to  traces  of  coloring-matter, 
and  sometimes  to  their  physical  conditions  only.  Tripoli 
consists  of  the  minute,  siliceous  shells  of  microscopic  plants, 
the  diatoms.  Siliceous  conglomerates  are  coarse  pebbles 
that  have  been  joined  by  deposited  silica.  The  silicates, 
such  as  feldspar,  mica,  and  certain  clays,  are  also  silicon 
compounds. 

Silicon  is  not  used  in  the  arts,  and  its  preparation  may 
be  omitted.  It  has  been  obtained  in  three  modifications, 
—  amorphous,  graphitoidal,  and  crystalline. 

Of  its  compounds  there  are  many.  Silica  is  the  most 
abundant.  The  silicates  are  a  series  of  compounds  of  very 
complex  constitution  not  very  well  understood.  Orthosilicic 
02 


BORON.  93 

acid,  H4SiO4,  has  not  been  separated.  Silicon  unites  with 
hydrogen  to  form  the  compound,  SiH4,  which  somewhat 
resembles  a  gaseous  compound  formed  by  phosphorus  and 
hydrogen,  in  that  it  is  spontaneously  inflammable. 

112.  Tests  for  Silicon  Compounds.  —  Natural  forms  of  sil- 
ica, as  quartz,  etc.,  are  readily  recognizable  by  their  phys- 
ical properties. 

2.  Silicates  in  solution  are  first  acidulated  with  hydro- 
chloric acid,  and   then  carefully  evaporated   to  dryness. 
The  dry  mass  is  then  dissolved  in  hydrochloric  acid.     If 
a  silicate  was  present,  it  will  now  be  reduced  to  a  white 
insoluble  powder,  SiOg,  which  is  insoluble  in   acids,  but 
soluble  in  potassium  hydroxide,  KOH. 

3.  An  insoluble  silicate  is  first  fused  with  sodium  car- 
bonate on  charcoal  and  then  treated  as  in  2. 


BORON. 

113.  Occurrence,  etc.  —  Boron  is  a  quite  plentiful  element 
which  occurs  only  in  compounds.  The  principal  boron 
compounds  are  boric  acid,  H3BO3;  borax,  Na2B4O7  + 10  H2O ; 
and  boracite,  2  Mg3B8O15,  MgCl2. 

Boric  acid  occurs  in  the  waters  of  certain  lagoons  in 
Tuscany.  Close  by  are  jets  of  volcanic  steam  which  are 
employed  to  evaporate  the  water,  from  which  crystalline 
boric  acid  is  deposited.  The  acid  is  purified  by  recrys- 
tallization. 

California  has  several  beds  of  native  borax.  These  beds 
are  on  the  sites  of  ancient  lakes,  long  since  dried  up. 
Boric  acid  is  obtained  from  this  borax  by  treatment  with 
hydrochloric  acid,  after  which  the  boric  acid  is  obtained 
by  crystallization. 


94  PHOSPHORUS. 

114.  Tests  for  Boric  Acid  and  its  Compounds.  —  1.  Free 
boric  acid  is  detected  in  solutions  by  dipping  in  it  a  strip 
of  turmeric  paper.     The  strip,  when  dried,  turns  brown, 
and  this  color  is  not  affected  by  dilute  hydrochloric  acid. 
Alkalies  also  affect  the  color  of  this  paper,  but  hydrochlo- 
ric acid  changes  the  color  produced. 

2.  A   borate    may  be   treated  with   hydrochloric    acid, 
which  frees  boric  acid.    The  next  step  is  the  same  as  in  1. 

3.  A  solid  borate  may  be  tested  by  the  flame  test  thus  : 
Make  a  bead  of  the  substance  on  a  loop  of  platinum  wire 
and  strongly  ignite  in  the  Bunsen  flame.     Now  moisten  the 
bead  with  sulphuric  acid  and  ignite  again.    Finally  moisten 
the  bead  with  glycerine  and  heat  strongly :  a  green  flame 
is  produced. 

PHOSPHORUS. 

115.  Occurrence,  etc.  —  Phosphorus  is  an  element  which 
occurs  widely  distributed,  but  never  in  the  free  state.     It 
occurs  in  the  older  igneous  rocks,  from  which  all  our  fer- 
tile soils  are  derived.     It  forms  with  calcium  the  minerals 
phosphorite,  Ca3(PO4)2,  and  apatite,  3  Ca3(PO4)2  +  CaFCl. 
With  iron  it  forms  vivianite,  Fe3(PO4)2  +  8  H2O.    Sombre- 
rite,  an  impure  form  of  calcium  phosphate,  furnishes  a  part 
of  the  phosphorus  of  commerce.     But  most  of  our  phos- 
phorus is  obtained  from  bones.    Animals  obtain  phosphorus 
from  plants,  and  plants  get  it  from  the  soil. 

Phosphorus  is  prepared  from  bone-ash.  The  first  step 
is  to  convert  the  ash  into  acid  calcium  phosphate,  which  is 
accomplished  by  using  sulphuric  acid :  — 

Ca8(P04)2  +  2  H2S04  =  CaH4(P04)2  +  2  CaS04. 

The  solution  of  acid  phosphate  is  evaporated  to  dryness 
and  ignited,  when  calcium  metaphosphate  is  obtained :  — 


PHOSPHORUS. 


95 


CaH4(P<  >4),  =  Ca(P03)2  +  2  H2O. 

The  metaphosphate  is  now  mixed  with  sand  and  charcoal, 
and  put  in  earthen  retorts  that  are  placed  in  tiers  in  a 
furnace,  and  so  arranged  that  their  necks  extend  outside 
and  dip  under  water  (Fig.  26).  When  heat  is  applied, 
phosphorus  is  liberated,  thus:  — 

2  Ca(P03)2  +  2  SiO,  +  IOC  =  2  CaSii  >,  +  10 CO  +  4  P. 

The  phosphorus  thus  ob- 
tained is  melted  under  wa- 
ter, and  strained  through 
chamois  leather,  to  remove 
coarse  impurities :  it  is 
further  purified  by  treat- 
ing it  with  sulphuric  acid 
and  potassium  dichromate, 
when  it  is  cast  in  sticks  of 
the  form  found  in  market. 

In  addition  to  the  ordi- 
nary waxy  form  of  phos- 
phorus found  in  the  ordi- 
nary sticks  of  commerce, 
two  other  modifications  are 
known.  When  common 
phosphorus  is  dissolved  in 
carbon  disulphide  and  the  FIG.  -»o. 

solution  is  allowed  to  evap- 
orate slowly,  octahedral  crystals  are  obtained.    Again,  when 
ordinary  or  crystalline  phosphorus  is  heated  to  240°  C.  in 
the  absence  of  oxygen,  red  or  amorphous  phosphorus  is 
obtained. 

Phosphorus  is  a  highly  inflammable  substance,  igniting 
at  low  temperatures.     In  consequence  of  this  property  it 


96  PHOSPHORUS    AND    HYDROGEN. 

is  used  in  large  quantities  as  an  ingredient  of  match-tips. 
The  inflammable  nature  of  phosphorus  may  be  safely 
shown  thus :  — 

EXP.  78.  Place  in  a  test-tube  a  bit  of  phosphorus  as  large 
as  a  kernel  of  wheat.  Dissolve  in  carbon  disulphide,  and  pour 
the  solution  over  a  piece  of  filter-paper.  Place  the  paper  on  a 
metallic  support,  and  in  a  short  time  the  disulphide  will  evap- 
orate, leaving  the  phosphorus  in  a  finely  divided  state,  and 
the  paper  will  soon  ignite  spontaneously. 

Phosphorus  is  a  substance  that  should  be  handled  with 
care.  It  should  always  be  taken  up  with  a  pair  of  pincers 
and  should  be  cut  under  water.  Upon  the  flesh  its  burns 
produce  deep  and  dangerous  wounds,  often  penetrating  to 
the  bone. 

The  peculiar  odor  and  the  physical  characteristics  of 
phosphorus  serve  to  identify  it. 


PHOSPHORUS    AND   HYDROGEN. 

116.  Phosphorus  and  hydrogen  form  three  compounds 
which  are  respectively,  gaseous,  liquid,  and  solid  sub- 
stances: PH3,  PH2,  and  P2H(?).  The  first  of  these  is 
often  called  phosphine,  and  its  preparation  will  be  given. 
None  of  these  compounds  are  of  great  importance  to  the 
beginner. 

EXP.  79.  Place  in  a  generating-flask  (Fig.  27)  a  strong  solu- 
tion of  potassium  hydroxide.  Drop  in  a  few  small  pieces  of 
phosphorus ;  and,  lastly,  add  a  small  quantity  of  ether,  for  the 
purpose  of  expelling  the  air  from  the  apparatus.  Insert  the 
delivery-tube,  heat  gently,  and  allow  the  bubbles  of  phosphine 
to  come  up  through  the  water.  On  striking  the  air,  the  gas 
will  be  found  to  be  spontaneously  inflammable,  forming  by  its 


PHOSPHORUS   AND   OXYGEN.  97 

combustion  rings  of  phosphorus  pentoxide  having  a  peculiar 
vortex  motion.     The  formation  of  the  gas  is  as  follows  :  — 

4  P  +  3  KOH  +  3  H20  =  3  KH2P02  +  PH3. 


PHOSPHORUS   AND    OXYGEN. 

117.    There  are  two  oxides  of  phosphorus :  viz.  P2O3  and 
P2O5.     The  first  is  obtained  when  phosphorus  is  burned  in 


FIG.  2; 


a  limited  supply  of  air,  and  the  second  when  the  air-sup- 
ply is  not  limited.  These  oxides  are  the  anhydrides  of 
phosphorous  and  phosphoric  acids. 

THE   PHOSPHOROUS    OXACIDS. 

118.    There  are  three  primary  acids  in  this  series  and  two 
others  that  are  derived  from  phosphoric  acid :  — 

Hypophosphorous  acid    .     .     .     H3P(X. 

Phosphorous  acid H3P03. 

Phosphoric  acid H3PC>4. 


98  THE   PHOSPHOROUS    OX  ACIDS. 

When  phosphoric  acid  is  heated,  water  is  driven  out;  and 
by  employing  suitable  temperatures  two  derived  acids  are 
to  be  had :  — 

Metaphosphoric  acid  ....     HP03. 

Pyrophosphoric  acid    ....     H4P207. 

The  basicity  of  hypophosphorous  and  phosphorous  acids 
merits  notice.  Hypophosphorous  acid  is  monobasic,  only 
giving  up  one  of  its  hydrogen  atoms.  Its  formula  might, 
therefore,  well  be  written,  HH2PO2.  Phosphorous  acid  is 
dibasic,  and  might  be  represented  by  the  formula,  H2HPO3. 
The  potassium  salts  of  these  acids  are,  for  example, 
KH2PO2  and  K2HPO3. 

Phosphoric  acid  merits  further  notice. 

EXP.  80.  Place  a  small  quantity  of  red  phosphorus  in  an 
evaporating-dish,  and  cover  with  reagent  nitric  acid.  Warm 
gently,  adding  more  nitric  acid  from  time  to  time,  until  the 
phosphorus  disappears  and  red  fumes  cease  to  come  off.  Now 
expel  the  excess  of  nitric  acid  by  heating  gently,  when  phos- 
phoric acid  is  obtained  as  a  syrupy  liquid. 

This  is  a  tribasic  acid  which  gives  up  one,  two,  or  three 
of  its  hydrogen  atoms.  Its  sodium  salts  serve  as  exam- 
ples: NaH2PO4,  Na2HPO4,  Na3PO4. 

119.  Tests  for  Phosphoric  Acid.  —  1.  To  the  solution  to  be 
tested  add  ammonia  and  ammonium  chloride.  A  clear 
solution  is  obtained.  Now  add  magnesium  sulphate, 
MgSO4,  and  a  white  crystalline  precipitate,  MgNH4PO4,  is 
obtained,  usually  after  standing  some  time. 

2.  Add  silver  nitrate  to  the  solution  to  be  tested.  A 
light  yellow  precipitate  is  obtained,  which  is  soluble  in 
ammonia,  nitric  acid,  and  in  acetic  acid. 

NOTE.  Make  both  tests  before  reporting  phosphoric  acid,  and  also  be 
sure  that  no  arsenic  acid  is  present. 


EXERCISES.  99 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  Test  a  sample  of  drinking-water  for  silicates  thus :  Acidulate  with 
hydrochloric  acid  one  half-litre  of  the  water  to  be  tested.    Now  evaporate 
strictly  to  dryness.     Again  dissolve  the  residue  in  hydrochloric  acid,  and 
then  examine  the  contents  of  the  dish  used  for  evaporating  the  water,  for 
the  white  powder,  SiO2. 

2.  Collect  some  of  the  sediment  from  the  bed  of  a  small  stream  and 
examine  with  a  microscope  for  the  shells  of  diatoms. 

3.  Collect  as  many  forms  of  silica  as  possible  and  describe  each 
form. 

4.  Why  are  siliceous  pebbles  mostly  rounded  and  smooth  ? 

5.  For  what  household  purposes  is  borax  used  ? 

6.  Burn  a  bit  of  bone  and  then  dissolve  the  ash  in  hydrochloric  acid. 
Now  add  ammonia,  and  note  the  precipitate  of  calcium  phosphate. 

7.  Test  the  salts  of  several  different  acids  for  their  acids.    Does  the 
salt  give  the  test  for  the  acid  from  which  the  salt  was  derived  ? 


CHAPTER   IX. 

INTRODUCTORY   TO   THE  METALS. 

120.  Properties  of  the  Metals.  —  Formerly  the  elements 
were  divided  into  two  groups,  —  the  Metals  and  the  Non- 
metals.  But  it  has  become  apparent  that  the  distinction 
is  not  well  founded.  The  elements  form  a  series  so  closely 
graded  in  properties  that  it  is  difficult  even  to  define  a 
metal.  But  in  general  we  may  say  that  a  metal  is  an 
element  which  possesses,  when  in  a  coherent  condition,  a 
peculiar  lustre,  termed  a  metallic  lustre.  Moreover,  the 
oxides  of  the  metals,  excepting  a  very  few  of  the  higher 
ones,  are  not  acid-forming. 

The  specific  gravities  of  the  metals  vary  from  that  of 
osmium,  22.48,  to  that  of  lithium,  0.59. 

The  specific  heat  of  a  metal  is  always  less  than  unity. 
It  has  been  found  that  when  the  specific  heat  of  an  ele- 
ment is  multiplied  by  the  atomic  weight  of  that  element  a 
nearly  constant  quantity  is  obtained,  viz.  6.4.  This  prod- 
uct is  termed  the  atomic  heat  of  an  element.  From  an 
inspection  of  the  results  so  obtained,  Dulong  and  Petit 
announced  the  law :  The  specific  heat  of  an  element  varies 
inversely  as  the  atomic  weight  of  that  element. 

While  the  law  is  but  approximately  true,  it  has  never- 
theless been  utilized  in  determining  the  atomic  weights  of 
some  of  the  rarer  elements.  In  order  to  do  this,  the  spe- 
cific heat  of  the  element  was  first  determined.  Some  of  its 
compounds  were  then  analyzed,  and  that  'atomic  weight 
100 


INTRODUCTORY   TO   THE   METALS.  101 

was  selected  which  would  give  a  product  of  about  6.4 
when  multiplied  by  the  specific  heat. 

The  melting-points  of  the  metals  vary  widely.  Thus 
mercury  melts  at  --40°  C.,  while  the  most  intense  heat 
obtainable  has  not  sufficed  to  melt  osmium. 

Metals  unite  in  definite  and  in  indefinite  proportions  to 
form  alloys.  Thus  brass  consists  of  zinc  and  copper  in 
varying  proportions.  Pewter  contains  four  parts  tin  and 
one  part  lead.  Alloys  are  found  extremely  useful,  since 
in  them  some  particular  requirement  may  be  obtained 
which  a  single  metal  does  not  possess. 

An  amalgam  is  an  alloy  of  a  metal  with  mercury. 

121.  Classification  of  the  Metals.  —  In  the  following  pages 
the  metals  are  classified  according  to  some  requirements 
in  analytical  work.  The  method  of  classification  may  be 
made  clear  by  supposing  a  solution  containing  a  salt  of 
each  of  the  common  metals.  To  this  solution  hydrochloric 
acid,  HC1,  is  to  be  added.  With  certain  of  these  metals 
the  acid  forms  insoluble  chlorides.  These  metallic  chlo- 
rides are  accordingly  precipitated  and  may  be  removed 
from  the  solution  containing  the  remaining  metals  by  fil- 
tration. The  metals  thus  precipitated  are  called  the 

FIRST  GROUP  METALS. 

Lead Pb. 

Silver Ag. 

Mercury Hg(ous). 

If  through  the  acid  filtrate  from  which  the  first  group 
metals  have  been  removed,  sulphuretted  hydrogen,  H2S, 
now  be  passed,  we  obtain  as  precipitates,  insoluble  in 
dilute  acids,  the  sulphides  of  the 


102  INTRODUCTORY  TO  THE  METALS. 

SECOND  GROUP  METALS. 

Arsenic As. 

Antimony Sb. 

Tin Sn. 

Bismuth Bi. 

Copper Cu. 

Cadmium Cd. 

Mercury .  Hg(ic). 

These  sulphides  can  now  be  filtered  out,  and  by  a  little 
judicious  treatment,  to  be  explained  further  on,  the  filtrate 
is  readily  prepared  for  the  separation  of  the  next  group. 
The  third  group  metals  are  precipitated  as  hydroxides  and 
sulphides  insoluble  in  the  presence  of  an  alkali  by  adding 
ammonia,  NH3,  ammonium  chloride,  NH4C1,  and  ammonium 
sulphide,  (NH4)2S.  Following  are 

THE  THIRD  GROUP  METALS. 

Iron Fe. 

Chromium    .          Cr. 

Aluminum Al. 

Nickel Ni. 

Cobalt Co. 

Manganese Mn. 

Zinc Zn. 

These  metals,  now  in  an  insoluble  compound,  may  be 
removed  from  the  solution  by  filtration,  and  the  filtrate 
by  appropriate  treatment  may  be  made  ready  for  the 
separation  of  the  next  group.  In  the  fourth  group  the 
metals  are  precipitated  as  carbonates  insoluble  in  alkalies 
by  adding  ammonia,  NH3,  ammonium  chloride,  NH4C1,  and 
ammonium  carbonate,  (NH4)2CO3. 


INTRODUCTORY   TO   $HE   METALS.  103 


THE  FOURTH  GROUP 


Barium   ........  Ba. 

Strontium    ..,,,..  Sr. 

Calcium  ........  Ca. 

Magnesium  .......  Mg. 

NOTE.  In  practice,  the  magnesium  is  removed  from  the  solution  from 
which  the  carbonates  of  the  first  three  metals  of  this  group  have  been 
separated  by  adding  disodium  phosphate,  Na.jHPO4.  This  precipitates 
the  magnesium  as  a  double  salt,  magnesium  ammonium  phosphate, 
MgNH4POi.  Magnesium  carbonate  is  soluble  even  in  alkalies. 

If  now  the  insoluble  compounds  of  the  fourth  group  be 
removed  by  filtration,  we  have  in  the  filtrate  only  the  fifth 
group  metals.  These  do  not  give  precipitates  with  ordi- 
nary reagents.  These  are  the 

FIFTH  GROUP  METALS. 

Potassium    ......     K, 

Sodium    .          .....     Na, 

and  the  radical  Ammonium  ......     NH4. 

By  following  the  plan  just  outlined,  the  metals  are  sep- 
arated into  groups.  Now  each  of  these  groups  can  be 
taken  up,  and  the  individual  metals  therein  can  be  sepa- 
rated from  one  another,  as  will  be  explained  in  appropriate 
places.  This  process  of  separation  and  identification  is 
termed  Qualitative  Analysis.  When  the  weights  of  the 
substances  present  in  a  compound  are  determined,  the 
process  is  termed  Quantitative  Analysis. 

We  are  now  ready  to  study  the  metals  in  detail. 


CHAPTER   X. 

THE    FIRST    GROUP   METALS. 

DATA  FOR  COMPUTATIONS.  —  LEAD:  Symbol,  Pb'' ;  Atomic  Weight,  207  ; 
Specific  Heat,  0.0315;  Melting-point,  334°;  Specific  Gravity,  11.37.— 
SILVER  :  Symbol,  Ag' ;  Atomic  Weight,  108  ;  Specific  Heat,  0.0570  ; 
Melting-point,  1000°;  Specific  Gravity,  10.53.  —  MERCURY  :  Symbol, 
Hg'- ";  Atomic  Weight,  200;  Specific  Heat,  0.0319  ;  Melting-point, 
-40°:  Boiling-point,  357.25°;  Specific  Gravity,  13.55. 


LEAD. 

122.  Occurrence  and  Preparation.  —  Metallic  lead  occurs 
only  in  insignificant  quantities.  Its  principal  ore  is 
galena,  PbS,  which  occurs  in  dark,  shining  cubes,  and  in 
other  forms  belonging  to  the  regular  system.  Nearly 
every  ore  of  lead  is  argentiferous,  i.e.  silver  bearing.  c 

EXP.  81.  Place  a  bit  of  galena 
(or  a  little  of  any  compound  con- 
taining lead)  in  a  shallow  cavity 
which  has  been  prepared  in  a  piece 
of  charcoal  (Fig.  28).  Cover  the 
substance  with  sodium  carbonate, 
Na2C03,  and  moisten  with  a  few 
drops  of  water.  Now  heat  the  sub- 
stance before  the  blow-pipe  reducing 
flame.  Bright  metallic  beads  will  be 
obtained.  Test  these  beads  thus : 

Place  oue  on  an  anvil  or  on  a  piece  of  iron,  and  strike  it 
lightly  with  a  hammer.     Is  it  malleable  ?     Brittle  ?     Cut  one 
of  the  beads  with  a  knife.     Is  it  hard  ?     Note  the  lustre  of 
104 


28. 


LEAD.  105 

the  beads,  and  draw  one  across  a  piece  of  white  paper.     Does 
it  leave  a  streak  ? 

Metallic  lead  is  largely  used  in  the  arts.  It  is  prepared 
by  heating  galena  in  a  limited  supply  of  air.  Sometimes  a 
reducing  agent  like  coal-dust  is  used  in  its  reduction. 

Ex.  Show  how  the  preceding  experiment  illustrates  these  processes. 
Name  the  uses  of  metallic  lead. 

123.  Properties  and  Compounds  of  Lead.  —  Lead  is  a  sil- 
very white  metal  which  soon  tarnishes  in  the  air.  It  is 
much  used  for  lead  pipes.  It  is  insoluble  in  pure  water, 
but  natural  waters  are  never  pure.  Hence  lead  pipes 
should  never  be  used  for  conveying  water  intended  for 
drinking  or  for  domestic  purposes.  Lead  salts  act  upon 
the  system  as  a  virulent,  cumulative  poison. 

Lead  dissolves  readily  in  nitric  acid,  forming  the  soluble 
salt,  Pb(NO3)2.  This  salt  and  the  acetate,  Pb(C2H3O2)2, 
when  dissolved  in  water  make  good  solutions  for  labora- 
tory practice. 

Some  of  the  compounds  of  lead  are  used  in  the  arts. 
We  notice  the  following: 

(a)  Lead  Oxide  or  Massicot,  PbO,  is  a  yellow  powder. 
Litharge  is  an  impure  form  of  lead  oxide.  These  are  pre- 
pared by  heating  lead  in  the  air.  Litharge  is  used  in  mak- 
ing flint  glass  and  in  glazing  earthenware.  Red  lead,  or 
minium,  Pb3O4,  is  used  as  a  pigment. 

(5)  White  lead  is  a  mixture  of  the  carbonate  and  hy- 
droxide of  lead.  This  is  the  best  white  paint,  and  is  pre- 
pared by  the  action  of  crude  acetic  acid  on  sheets  of  lead 
that  are  placed  in  earthen  crocks  and  covered  with  ma- 
nure or  spent  tan  bark.  The  decomposing  manure  fur- 
nishes the  carbon  dioxide  necessary  to  convert  the  acetate, 
first  formed,  into  white  lead. 


106  SILVER. 

(c)  Lead  Acetate,  Pb(C2H3O2)2,  is  much  used  in  medi- 
cine.    It  is  also  used  as  a  reagent  in  the  laboratory.     It 
may  be  obtained  by  the  action  of  acetic  acid  on  metallic 
lead.     Lead  acetate  is  used  in  dyeing,  as  shown  in  the 
following  experiment :  — 

EXP.  82.  Moisten  a  strip  of  white  cotton  cloth  in  a  solu- 
tion of  lead  acetate.  Now  moisten  in  potassium  dichromate 
solution,  K2Cr207.  What  color  is  the  strip  dyed  ? 

(d)  Lead   Chloride,  PbCL,  is  a  precipitate  met  with  in 
the  course  of  analysis.     It  is  a  white  crystalline  substance, 
soluble  in  hot  water. 

(<?)  Chrom.e  Yellow,  PbCrO4,  is  used  as  a  pigment.  It 
is  obtained  when  potassium  dichromate  is  added  to  a  sol- 
uble lead  salt. 

124.  Tests  for  Lead. — 1.  Metallic  lead  is  recognized  by 
its  physical  properties,  or  the  metal  is  dissolved  in  nitric 
acid  and  tested  as  in  2. 

2.  Lead  in  a  solution  of  its  salts  is  recognized  by  the 
color  of  its  precipitates  :  — 

K2O207  gives  PbO04,  yellow. 
KI  gives  PbI2,  yellow  scales. 
H2S04  gives  PbS04,  white. 
H2S  gives  PbS,  black. 

3.  A  solid  may  be  tested  before  the  blow-pipe.     The 
beads  obtained  are  then  dissolved  in  nitric  acid  and  tested 
by  2. 

SILVER. 

125.  Occurrence  and  Preparation.  —  Native  metallic  silver 
occurs  in  considerable  quantities  along  with  native  copper 
deposits.     Most  of  the  silver  of  commerce  comes,  however, 


SILVER.  107 

from  the  lead-furnaces.  There  are  some  ores  of  silver 
such  as  argentite,  Ag2S,  and  horn  silver,  AgCl.  Silver 
also  occurs  in  connection  with  other  nietals  and  combined 
with  arsenic  and  sulphur. 

EXP.  83.  Place  a  zinc  strip  in  a  test-tube  containing  a 
solution  of  silver  nitrate.  Note  the  dark  deposit  that  soon 
collects  011  the  zinc,  and  then  remove  it  to  a  piece  of  charcoal, 
and  heat  it  before  the  blow-pipe.  Try  the  bead  as  you  tried 
lead.  Complete  this  equation  •  — 


EXP.  84.  Add  hydrochloric  acid  to  a  solution  of  silver 
nitrate.  Collect  the  precipitate,  AgCl,  on  charcoal,  and  heat 
in  the  blow-pipe  flame.  Do  you  obtain  a  silver  bead  ? 

Silver  is  obtained  from  the  lead-furnaces  according  to 
the  following  process:  The  silver  is  present  in  the  lead 
ores  in  very  small  quantities.  But  the  same  process  that 
reduces  the  lead  also  reduces  the  silver.  Now  the  lead  is 
allowed  to  cool  in  large  tanks.  During  the  cooling  process 
pure  crystals  of  lead  separate  out,  and  these  are  removed. 
By  repeating  this  process,  an  alloy  is  obtained  at  last  that 
is  rich  in  silver. 

This  alloy  is  now  heated  in  bone-ash  vessels,  called 
ki  cupels,"  over  which  a  current  of  air  is  passing.  In  this 
way  the  lead  is  oxidized  and  absorbed  by  the  cupels,  leav- 
ing pure  silver.  This  process  is  called  cupellation. 

Other  processes  of  reducing  silver,  of  less  importance 
to  the  beginner,  are  also  employed  to  some  extent. 

126.  Properties  and  Compounds.  —  Silver  has  long  been 
esteemed  as  one  of  the  precious  metals.  It  is  a  bright 
metal  that  does  not  oxidize  in  the  air  at  any  temperature  ; 
hence  its  use  for  jewelry  and  coinage.  Some  substances 
like  sulphur,  chlorine,  bromine,  etc.,  cause  silver  to  tarnish. 


108  SILVER. 

Ex.  Why  do  coins  carried  in  the  pockets  with  matches,  blacken.  Ex- 
plain the  tarnishing  of  egg-spoons  and  mustard-spoons.  Why  should  silver 
drinking- cups  not  be  used  at  sulphur  springs  ?  Name  the  uses  of  silver. 

Silver  dissolves  rapidly  in  nitric  acid,  affording  silver 
nitrate,  AgNO3.  This  salt  is  much  used  as  a  reagent,  and 
is  the  best  one  for  working  purposes  in  the  laboratory. 

Some  of  the  compounds  of  silver  are :  — 

(a)  Silver  Nitrate,  or  Lunar  Caustic,  AgNO3.  This  salt 
has  just  been  mentioned.  It  is  used  in  medicine  and  in 
photography. 

(6)  Silver  Chloride,  AgCl,  is  the  precipitate  obtained  by 
adding  the  group  reagent,  HC1,  to  a  solution  of  a  silver 
salt.  It  is  sofuble  in  ammonia. 

(r?)  A  silver-plating  solution  can  be  prepared  thus : 
Precipitate  silver  nitrate  with  a  solution  of  common  salt, 
NaCl.  Filter,  and  wash  the  precipitate  quickly  in  pure 
water.  Now  dissolve  the  precipitate  in  an  excess  of  potas- 
sium cyanide,  KCN,  when  the  solution  is  ready  for  use. 
These  equations  explain  the  steps  involved :  — 

AgN03  +  NaCl  =  AgCl  +  NaN03 ; 
AgCl  4-  2  KCN  =  AgCN,  KCN  +  KC1. 

127.  Tests  for  Silver.  —  Metallic  silver  is  recognized  by 
its  physical  properties.  But  it  may  be  dissolved  in  nitric 
acid,  and  identified  as  in  2. 

2.  Silver  in  solutions  of  its  salts  may  be  recognized  by 
the  color  of  its  precipitates  as  follows  :  — 

Hydrochloric  acid,  HC1,  gives  AgCl,  white  (sol.  in  ammonia). 
Potassium  dichromate,  K2Cr207,  gives  AgCr04,  red. 
Hydrogen  sulphide,  H2S,  gives  Ag2S,  black. 
Potassium  iodide,  KI,  gives  Agl,  light  yellow. 

3.  A  solid  may  be  reduced  before  the  blow-pipe,  and  the 
bead  dissolved  in  nitric  acid,  and  tested  as  in  2. 


MERCURY.  109 


MERCURY. 

128.  Occurrence  and  Preparation.  —  Mercury  occurs  free 
in  small  drops  disseminated  through  its  principal  ore,  cin- 
nabar, HgS.  The  artificial  sulphide  is  known  as  the  pig- 
ment vermilion. 

EXP.  85.  Place  a  bit  of  cinnabar  in  a  hard  glass  tube  open 
at  both  ends.  Hold  the  tube  somewhat  slanting  in  the  Bunsen 
flame,  and  heat  strongly.  Note  the  fumes  escaping  from  the 
upper  end  of  the  tube.  Also  note  the  metallic  mirror  formed 
on  the  sides  of  the  tube  a  short  distance  above  the  cinnabar. 
The  reaction  is  :  — 


/c 

The  preparation  of  mercury  for  commerce  is  a  very  sim- 

ple operation.  The  ore,  cinnabar,  is  simply  heated  in  a 
current  of  air.  The  sulphur  is  oxidized  to  the  dioxide,  and 
mercury  is  set  free  in  the  form  of  vapors  which  are  con- 
densed in  suitable  condensers. 

129.  Properties  and  Compounds.  —  Mercury  is  a  silver- 
white  liquid  which  slowly  passes  into  a  vapor  at  all  tem- 
peratures between  its  freezing-point  and  boiling-point.  It 
is  largely  used  in  making  philosophical  instruments  and  in 
making  amalgams.  On  the  system,  the  vapors  of  mercury 
act  as  a  poison.  This  metal  has  been  known  since  the  high- 
est antiquity,  and  its  compounds  have  been  largely  utilized. 
The  most  common  compounds  of  mercury  are  :  — 

(#)  Red  Oxide  of  Mercury,  HgO,  is  used  in  medicine. 
It  is  prepared  by  heating  a  mixture  of  mercury  and  mer- 
curic nitrate  until  red  fumes  cease  to  come  off.  When 
sodium  or  potassium  hydroxide  is  added  to  a  salt  of  mer- 
cury, the  same  oxide  is  obtained,  but  the  color  is  yellow  in 
this  case. 


110  MERCURY. 

(b)  Mercurous  Chloride,  or  Calomel,  Hg2Cl2,  is  used  in 
medicine.  It  is  prepared  by  subliming  an  intimate  mixture 
of  mercuric  chloride  and  mercury.  It  is  also  obtained  as 
a  group  precipitate  when  hydrochloric  acid  is  added  to  a 
soluble  mercurous  salt.  This  precipitate  turns  black  when 
moistened  with  ammonia.  It  is  soluble  in  nitro-hydro- 
chloric  acid. 

(<?)  Mercuric  Chloride,  or  Corrosive  Sublimate,  HgCl2,  is 
a  deadly  poison.  It  is  used  in  the  laboratory  as  a  reagent. 
It  is  prepared  by  subliming  a  mixture  of  mercuric  sulphate 
and  common  salt  :  — 


HgS04  +  2  NaCl  =  HgCl2 

(d)  Mercurous  Nitrate,  Hg2(NO3)2,  is  prepared  by  acting 
on  an  excess  of  metallic  mercury  with  cold  dilute  nitric 
acid.  If  the  acid  be  in  excess,  mercuric  nitrate,  Hg(NO3)2, 
is  formed.  Mercurous  nitrate  is  a  good  working  com- 
pound for  laboratory  purposes. 

It  will  be  noticed  that  mercury  forms  two  compounds 
with  hydrochloric  acid,  Hg2Cl2  and  HgCl2  ;  also  two  com- 
pounds with  nitric  acid  are  to  be  had,  Hg2(NO3)2  and 
Hg(NO3)2.  These  compounds  are  called  respectively  mer- 
GUTOUS  and  mercuric  salts.  If  we  were  to  examine  all  the 
compounds  of  mercury,  we  should  find  that  with  every  acid 
two  salts  are  formed.  These  would  correspond  to  the  mer- 
curous and  mercuric  salts  formed  with  hydrochloric  and 
nitric  acids.  Those  compounds  containing  the  least  pro- 
portion of  the  acid  constituent  are  called  mercurows  com- 
pounds, while  those  with  the  greater  proportion  of  the  acid 
are  the  rnercur^  compounds. 

It  will  be  noticed  that  in  the  mercurous  salts  two  atoms 
of  mercury  appear.  These  taken  together  are  equivalent 
to  a  diad,  while  in  the  mercuric  compounds  one  atom  is  a 


MEBCTTRY.  Ill 

diad.  It  is  customary  to  write  all  mereurous  compounds 
with  an  even  number  of  atoms.  Mereurous  salts  only  are 
precipitated  in  the  first  group. 

Besides  mercury  there  are  other  metals  which  form  two 
classes  of  compounds,  iron,  tin,  and  copper  being  the  most 
prominent. 

130.  Tests  for  Mercury.  —  1.  Metallic  mercury  is  readily 
recognized  by  its  physical  properties. 

2.  Mercury  in  solutions  of  mereurous  salts  is  detected  by 
adding  hydrochloric  acid,  which  gives  the  white  precipi- 
tate, Hg2Cl2.     This  precipitate  turns  black  by  the  addition 
of  ammonia. 

3.  Mercury  in  solutions  of  mercuric  salts  is  tested  by 
adding  stannous  chloride,  SnCL.     At  first  a  white  precipi- 
tate, Hg2Cl2,  is  formed,  which  changes  to  gray,  and  finally 
to  black.    By  warming  this  precipitate  and  rubbing  it  with 
a  glass  rod,  minute  beads  of   metallic  mercury  may  be 
obtained.     It  usually  requires  some  time  for  these  changes 
to  take  place  in  this  precipitate.     The  action  of  the  tin 
salt  is  as  follows  :  — 

8nCl2  +  HgCL  =  SnCl4  +  Hg. 

4.  If  a  clean  copper  wire  be  introduced  into  a  solution 
of   either   a  mereurous  or  a  mercuric  salt,  a  coating  of 
metallic  mercury  is  obtained  on  the  wire. 

131.  Separation  and  Identification  of  the  First  Group  Metals. 
—  As  previously  explained,  the  first  group  metals  are  sep- 
arated from  all  others  by  adding  hydrochloric  acid  to  a 
solution  containing  salts  of  these  metals.     The  chlorides, 
PbCl2,  AgCl,  and  Hg2Cl2,  are  thus  obtained  as  a  precipitate. 
These  insoluble  chlorides  are  now  filtered  out,  and  as  they 
lie  on  the  filter-paper,  washed  by  pouring  over  them  a  little 


112  MERCURY. 

cold  water.     This  leaves  them  clean  and  still  lying  on  the 
filter-paper.     Now  proceed  by  1. 

1.  Add  much  hot  water  to  the  chlorides.    Lead  chloride 
alone  is  dissolved,  and  the  solution  runs  through  the  filter- 
paper,  and  is  to  be  collected  in  a  suitable  dish,  such  as  a 
small  beaker-glass.     Now  test  this  solution  by  Art.  124,  2. 
In  this  way  the  lead  is  identified.     Now  proceed  by  2. 

2.  The  chlorides  of  silver  and  mercury  remain  on  the 
filter-paper.     So  add  ammonia,  and  thus  dissolve  the  silver 
chloride.     Save  the  filtrate  as  before,  and  turn  it  back  on 
the  filter-paper  once  or  twice  to  insure  the  complete  solu- 
tion of  the  silver  chloride.     Now  to  the  filtrate  add  nitric 
acid  to  an  acid  reaction  with  blue  litmus  paper.     The  sil- 
ver will  be  again  precipitated  as  AgCl.     In  this  connec- 
tion this  precipitate  is  a  sufficient  guarantee  of  the  presence 
of  silver.     But  if  the  precipitate  be  plentiful,  it  may  be 
collected  on  charcoal  and  reduced  to  a  silver  bead  before 
the  blow-pipe.     Now  proceed  by  3. 

3.  At  the  same  time  the  silver  chloride  was  dissolved  in 
ammonia,  the  mercurous  chloride  was  turned  black  by  the 
action  of  the  ammonia.     Nb  further  identification  of  the 
mercury  is  necessary  in  this  connection.     If  the  student 
so  desires,  he  may  dissolve  this  black  precipitate  in  nitro- 
hydrochloric  acid  and  test  it  by  adding  SnCl2,  Art.  130,  3. 

GENERAL  NOTE.  Since  lead  chloride  dissolves  so  easily,  some  lead 
always  goes  over  into  the  second  group.  It  is  necessary  that  the  solution 
be  cold  when  the  hydrochloric  acid  is  added. 

EXERCISES. 

(For  Review  or  Advanced  Course.} 

1.  Compute  the  atomic  heat  of  lead,  of  silver,  and  of  mercury. 

2.  Arrange  the  formulae  of  all  the  acids  previously  studied  in  a  vertical 
column  at  the  left  side  of  a  sheet  of  paper.    At  the  right  of  each  acid  write 


EXERCISES.  113 

the  formula  of  the  salt  which  that  acid  forms  with  lead.  At  the  right  of 
the  lead  salts  write  the  formulae  of  the  silver  salts.  Make  two  columns 
for  mercury,  and  in  the  first  write  the  mercurous  salts,  and  in  the  second 
write  the  mercuric  salts.  Now  name  all  the  salts  written. 

3.  Write  the  equation  for  the  solution  of  metallic  lead  hi  nitric  acid, 
knowing  that  Pb(NO3)2,  NO.  and  H20  are  the  products  of  the  reaction. 

4.  Write  the  reactions  for  hydrochloric  acid  and  the  following  salts  : 
Pb(N03)2,  AgN03,  and  Hg2(NO2)2. 

5.  Try  the  effect  of  a  strip  of  zinc  on  a  solution  of  a  salt  of  lead  ; 
upon  a  salt  of  mercury.     Write  the  reactions. 


CHAPTER   XL 

THE   SECOND   GROUP  METALS. 

DATA  FOR  COMPUTATIONS.  —  ARSENIC  :  Symbol,  As'"'  v  ;  Atomic  Weight, 
75  ;  Specific  Heat,  0.0822  ;  Melting-point,  356°  ;  Specific  Gravity,  6.78. 

—  ANTIMOXV:  Symbol,  Sb'"'  v  ;   Atomic  Weight,  120;  Specific  Heat, 
0.0523;  Melting-point,  425°;  Specific  Gravity,  0.71.  — TIN:    Symbol, 
Sn".  ""  ;  Atomic  Weight,  118 ;  Specific  Heat,  0.0548 ;  Melting-point, 
230° ;  Specific  Gravity,  7.29.  — BISMUTH  :  Symbol,  Bi'"  ;  Atomic  Weight, 
210  ;  Specific  Heat,  0.0305  ;  Melting-point,  270°  ;  Specific  Gravity,  9.80. 

—  COPPER  :  Symbol,  Cu'.  "  ;  Atomic  Weight,  63  ;  Specific  Heat,  0.0952  ; 
Melting-point,  1090°  ;  Specific  Gravity,  8.95.  —  CADMIUM  :  Symbol,  Cd"; 
Atomic   Weight,    112 ;    Specific   Heat,    0.0567  ;    Melting-point,    315° ; 
Specific  Gravity,  8.60. 

132.  The   second  group  metals   yield  sulphides  insolu- 
ble in  dilute  acids.     These  sulphides   are   obtained  from 
solutions  after  the  removal  of  the  first  group  metals,  as 
previously  explained.     Since  the  sulphides  of  arsenic,  anti- 
mony, and  tin  are  soluble  in  yellow  ammonium  sulphide, 
(NH4)2S,  these  metals  may  be  regarded  as  forming  a  sub- 
group, and  in  analysis  they  are  separated  from  bismuth, 
copper,  and  cadmium  by  the  addition  of  this  reagent  to 
the  sulphides  of  the  whole  group. 

ARSENIC. 

133.  Occurrence  and  Preparation.  —  Metallic  arsenic  oc- 
curs native  in  kidney-shaped  masses  of  a  laminated  struc- 
ture.    But  most  of  our  arsenic  is  prepared  from  the  ores, 
orpirnent,  As2S3,  and  mispickel,  ( 

114 


ARSENIC.  115 

EXP.  86.  Make  a  pellet  of  arsenic  trioxide,  As203,  with 
powdered  charcoal  and  a  drop  or  two  of  water.  Place  the 
pellet  in  the  bottom  of  a  hard  glass  test-tube,  and  heat  gently, 
to  expel  the  moisture.  Now  drop  into  the  tube  a  loosely  fit- 
ting cork  of  chalk,  and  then  heat  the  pellet  strongly.  Note 
the  deposit  of  arsenic  on  the  sides  of  the  tube  above  the  chalk. 

Arsenic  is  prepared  for  commerce  by  heating  its  ores  in 
earthen  tubes.  The  vapors  of  arsenic  are  condensed  in 
iron  condensers.  The  arsenic  thus  obtained  is  purified  by 
subliming  it  with  charcoal.  As  thus  prepared  it  forms 
rhombohedral  crystals  possessing  a  bright  metallic  lustre. 

134.  Properties  and  Compounds.  —  Arsenic  is  a  bright 
solid  which  oxidizes  quite  readily  in  warm,  moist  air, 
forming  a  dark  substance  known  as  fly-powder.  Under 
ordinary  pressures,  arsenic  seems  to  vaporize  without  melt- 
ing, at  356°.  Under  greater  pressure  it  may  be  obtained 
in  the  liquid  form. 

Both  arsenic  and  its  soluble  compounds  act  as  deadly 
poisons  when  taken  into  the  system.  It  matters  not 
whether  the  arsenic  be  taken  internally  or  whether  it  be 
absorbed  by  the  lungs  or  through  the  pores  of  the  skin  in 
the  form  of  dust  or  vapor,  the  action  is  the  same.  Wall- 
paper or  carpets  colored  with  arsenic  compounds  are  almost 
certain  to  bring  on  the  symptoms  of  arsenic  poisoning. 

Arsenic  stands  midway  in  its  properties  between  the 
metals  and  the  non-metals.  In  its  chemical  compounds  it 
is  closely  allied  to  phosphorus,  while  in  its  physical  prop- 
erties it  resembles  antimony. 

The  metal  arsenic  can  be  brought  into  solution  by  treat- 
ing it  with  nitro-hydrochloric  acid  or  with  chlorine  water. 
Arsenic  acid  is  thus  obtained  :  - 

2  As ,+  5  01, +  8  H2O  =  2  H8As04  +  10  HC1. 


116  ARSENIC. 

Arsenic  trioxide,  As2O3,  is  soluble"  in  potassium  or  sodium 
hydroxide,  thus :  — 

As2O3  +  6  NaOH  =  2  N%As03  +  3  H20  4-  an  excess  of  NaOH. 

The  sodium  arsenite  thus  formed  is  soluble  in  water. 
Some  of  the  compounds  of  arsenic  follow :  — 
(a)  Arsenic  Trioxide,  As2O3,  is  a  white  substance  usually 
sold  in  drug  stores  under  the  name  "  arsenic."     It  is  used 
in  medicine  and  in  taxidermy.     It  is  supposed  to  be  the 
anhydride  of  Arsenious  Acid,  H3AsO3,  which  has  not  been 
isolated.     The  arsenites  are  known. 

(5)  Scheele's  G-reen  or  Copper  Arsenite,  CuHAsO3,  and 
iSchweinfurth9 s  G-reen  or  Copper  Aceto-arsenite,  (CuO As2O3)3, 
Cu(C2H3O2)2  are  used  as  pigments,  and  both  are  sold  under 
the  name  "  Paris  green."  These  substances  as  well  as 
London  purple,  another  somewhat  similar  compound  of 
copper  and  arsenic,  are  extensively  used  as  insecticides. 

(c)  Arsenic  Pentoxide,  As2O5,  may  be  considered  to  be 
the  anhydride  of  Arsenic  Acid,  H3AsO4.     The  pentoxide  is 
to  be  had  by  treating  arsenic  with  strong  nitric  acid.    Arse- 
nic acid  has  already  been  mentioned. 

(d)  Arsenious  Sulphide,  As2S3,  is  the  precipitate  obtained 
in  the  regular  course  of  analysis.     It  is  soluble  in  yellow 
ammonium  sulphide. 

135.  Tests  for  Arsenic.  —  1.  A  solid  substance  containing 
arsenic,  when  heated  on  charcoal  before  the  blow-pipe  reduc- 
ing flame,  yields  vapors  having  an  odor  resembling  garlic. 

2.  When  hydrogen  sulphide  is  passed  through  a  solu- 
tion  containing  arsenic,  the  yellow  precipitate,  As2S3,  is 
obtained. 

3.  A  solid  or  a  solution  is  best  tested  for  arsenic  by  the 
spot-test,  thus  :    The  substance  supposed  to  contain  arsenic 


ARSENIC.  117 

is  placed  in  an  evaporating-dish,  and  a  crystal  of  potassium 
chlorate  and  hydrochloric  acid  are  added.  Heat  is  now 
applied,  when  the  arsenic,  if  any  be  present,  is  oxidized  to 
arsenic  acid.  The  boiling  is  continued  until  the  excess  of 
chlorine  is  driven  off. 

In  a  generating-flask  place  some  arsenic-free  zinc,  and 
water.  Add  sulphuric  acid,  and  if  hydrogen  gas  is  not 
freely  given  off,  add  a  crystal  of  pure  copper  sulphate, 
which  will  cause  a  copious  evolution  of  hydrogen.  As 
soon  as  the  apparatus  is  free  from  air,  add  the  solution  to 
be  tested  as  now  prepared  in  the  evaporating-dish.  Imme- 
diately insert  a  jet  delivery-tube  and  ignite  the  stream  of 
escaping  gas,  AsH3,  and  direct  the  flame  against  a  cold 
porcelain  surface.  If  arsenic  be  present,  a  steel-gray  spot 
or  mirror  will  be  obtained  on  the  porcelain.  Make  sev- 
eral spots,  and  make  sure  that  they  are  arsenic,  thus :  — 

(#)  Test  one  of  the  spots  with  yellow  ammonium  sul- 
phide ;  it  turns  yellow. 

(6)  Test  another  with  a  drop  of  hydrochloric  acid ;  it 
does  not  dissolve. 

(c)  Add  to  another  a  drop  of  a  solution  made  by  adding 
potassium  hydroxide  to  chlorine  water ;  it  dissolves. 

(d)  Treat  another  with   hot   nitric   acid;   it   dissolves 
clear.     Add  to  this  solution  a  drop  of  silver  nitrate ;  no 
change  in  color  occurs.     Now  place  the  tip  of  a  blow-pipe 
at  the  mouth  of  an  uncorked  ammonia  bottle  and  force  a 
stream  of  ammonia  gas  against  the  same  solution ;  it  turns 
brick-red  or  yellow.     You  are  now  certain  that  arsenic  in 
some  form  is  present. 

4.  An  arsenate  can  be  distinguished  from  an  arsenite, 
thus :  To  the  solution  to  be  tested  add  magnesium  sul- 
phate, MgSO4.  A  precipitate  may  be  either  an  arsenate  or 


118  ANTIMONY. 

an  arsenite.  Now  add  ammonia  and  ammonium  chloride. 
If  the  precipitate  dissolves,  it  is  an  arsenite  ;  if  it  does  not 
dissolve,  it  is  an  arsenate. 

NOTE.     Be  sure  that  phosphates  are  absent  before  applying  this  test. 

ANTIMONY. 

136.  Occurrence    and    Preparation.  —  Metallic    antimony 
occurs  in  small  scaly  masses,  which  also  contain  as  impuri- 
ties, iron,  silver,  etc.     But  the  chief  source  of  antimony  is 
the  ore,  stibnite,  Sb2S3. 

EXP.  87.  Make  a  pellet  of  any  antimony  compound  with 
sodium  carbonate,  and  moisten  with  a  drop  of  water.  Place 
the  pellet  on  charcoal,  and  heat  before  the  reducing  blow-pipe 
flame.  A  bright  bead  is  obtained.  Test  this  bead  as  in  the 
case  of  lead. 

Antimony  is  prepared  for  commerce  by  heating  stibnite 
in  vessels  with  perforated  bottoms.  The  sulphide  melts  and 
runs  through  pure.  It  is  next  heated  with  metallic  iron, 
which  unites  with  the  sulphur  and  sets  the  antimony  free. 

137.  Properties  and  Compounds.  —  Antimony  is  a  bluish 
white  metal,  so  brittle  that  it  may  be  ground  to  a  dust. 
It  is  used  principally  in  making  alloys,  to  which  it  imparts 
hardness  and  the   property   of   expanding  when   cooling. 
Large   quantities   of  antimony  are   used  in  making  type 
metal.     Antimony  is   also   used   in   some    pharmaceutical 
preparations. 

With  acids  antimony  forms  salts,  in  which  it  acts  like  a 
triivalent  metal  as  in  antimony  trichloride,  SbCl3.  The 
group,  SbO,  forms  basic  salts,  in  which  it  acts  as  a  monad. 
The  salts  thus  formed  are  called  antimonyl  salts.  Anti- 
monyl  sulphate,  (SbO)2SO4,  will  serve  as  an  example. 


ANTIMONY.  119 

Antimony  also  acts  like  an  acid-forming  element.  An- 
timonic  acid,  H3SbO4,  is  the  principal  antimony  acid.  This 
acid  closely  resembles  phosphoric  and  arsenic  acids. 

Hot  nitro-hydrochloric  acid  dissolves  metallic  antimony, 
yielding  antimony  trichloride,  SbCl3.  When  dissolved  in 
water  acidulated  with  hydrochloric  acid,  this  chloride 
makes  a  good  working  solution  for  laboratory  practice. 

Some  of  the  antimony  compounds  follow :  - 

(a)  The  oxides,  Sb2O3,  Sb2O4,  and  Sb2O5,  give  rise  to  ti 
series  of  acids  similar  to  those  of  phosphorus. 

(£>)  Tartar  Emetic,  C4H4KSbO7,  is  used  in  medicine.  It 
is  prepared  by  dissolving  antimony  trioxide  in  potassium 
tartrate,  KHC4H4O6. 

(c~)  Antimony  Trisulphide,  SboSs,  is  the  orange-colored 
precipitate  obtained  in  the  course  of  analysis.  It  is  solu- 
ble in  yellow  ammonium  sulphide. 

138.  Tests  for  Antimony.  —  1.  Any  antimony  compound 
when  heated  on  charcoal  with  sodium  carbonate  yields  a 
bright,  brittle  bead  of  metallic  antimony. 

2.  Any  solution  of  an  antimony  salt  gives  with  hydro- 
gen sulphide  an  orange-colored  precipitate,  Sb2S3. 

3.  Antimony  compounds  may  be  placed  in  a  generating- 
flask  with  zinc  and  sulphuric  acid,  and  the  escaping  gas, 
SbH3,  may  be  ignited  as  soon  as  the  apparatus  is  free  from 
air  and  the  flame  directed  against  a  cold  porcelain  surface. 
Black  or  velvety  brown  spots  of  antimony  are  obtained. 
These  spots  may  be  distinguished  from  arsenic  thus :  - 

(a)  An  antimony  spot  with  yellow  ammonium  sulphide 
turns  orange. 

(b)  With  hot  nitric  acid  it  turns  white. 

(<?)  With  a  drop  of  a  solution  of  potassium  hydroxide 
in  chlorine  water  it  is  insoluble. 


120  TIN. 

(df)  The  white  spot  formed  in  (&),  when  treated  with  sil- 
ver nitrate  and  ammonia  vapor,  gives  no  color ;  but  when 
a  drop  of  ammonia  solution  is  added,  it  turns  black. 


TIN. 

139.  Occurrence  and  Preparation.  —  But  small  quantities 
of  tin  occur  native.  Commercial  tin  is  obtained  from  the 
ore,  tin  stone  or  cassiterite,  SnO2.  This  ore  occurs  in 
veins  in  the  older  schistose  and  crystalline  rocks.  It  is 
also  found  in  nodules  in  the  beds  of  rivers  flowing 
through  these  regions.  As  thus  found  it  is  popularly 
called  "  stream  tin."  The  oldest  tin  mines  are  in  Corn- 
Avall,  England,  but  it  is  now  mined  in  Australia,  Bolivia, 
Peru,  and  in  the  Black  Hills  in  South  Dakota. 

EXP.  88.  Make  a  paste  of  a  tin  compound  with  solid  potas- 
sium cyanide  and  a  drop  of  water.  Heat  this  paste  on  char- 
coal in  the  reducing  flame.  Small  beads  of  tin  are  obtained 
with  great  difficulty.  If  the  oxidizing  flame  be  used,  a  coating 
of  stannic  oxide  will  be  formed  around  the  assay,  which  is  pale 
yellow  while  hot  and  white  when  cold. 

In  the  commercial  preparation  of  tin,  the  tin  stone  is 
first  crushed  fine  and  then  washed  to  remove  some  of  the 
impurities.  It  is  then  further  purified  by  roasting  it  in 
revolving  inclined  cylinders  through  which  a  blast  of  air 
is  passing.  In  this  way  volatile  substances,  such  as  arsenic 
and  sulphur,  are  driven  off  while  other  impurities  are  oxi- 
dized. The  ore  is  now  washed  again  and  thus  obtained 
quite  pure.  The  pure  ore  is  now  mixed  with  anthracite 
coal  and  reduced  in  a  blast-furnace.  The  tin  thus  obtained 
is  now  drawn  off  and  purified  by  liquation  ;  i.e.  it  is  grad- 
ually melted  in  a  reverberatory  furnace.  Since  the  pure 


TIN.  121 

tin  is  more  fusible  than  its  alloys,  it  melts  first,  and  is  drawn 
off  and  stirred  with  poles  of  green  wood;  a  dross  sepa- 
rates, thus  leaving  the  tin  in  a  state  of  great  purity. 

140.  Properties  and  Compounds  of  Tin.  —  Tin  is  a  white, 
malleable  metal,  the  lustre  of  which  is  quite  permanent 
in  the  air  at  ordinary  temperatures.    It  is  extensively  used 
as  tin  foil  and  for  coating  thin  sheets  of  iron  to  form  tin 
plate.     When  alloyed  with  lead,  solder  is  formed. 

Tin  as  a  base  forms  two  series  of  salts,  the  stannous  and 
the  stannic  compounds.  It  also  forms  acids  of  small 
importance. 

Tin  reacts  with  hydrochloric  acid  to  form  stannous  chlo- 
ride, SnCl2.  With  nitro-hydrochloric  acid  containing  an 
excess  of  hydrochloric  acid,  stannic  chloride,  SnCl4,  is  ob- 
tained. Solutions  of  these  salts  are  useful  for  laboratory 
practice. 

Some  of  the  compounds  of  tin  follow :  — 

(a)  Stannic  Acid,  H2SnO3,  is  obtained  when  calcium 
carbonate  is  treated  with  an  excess  of  stannic  chloride. 
Sodium  Stannate,  Na2SnO3,  is  largely  used  as  a  preparing 
salt  in  calico-printing. 

(5)  Stannous  Sulphide,  SnS,  is  a  brown  substance,  while 
Stannic  Sulphide,  SnS2,  is  a  yellow  one.  These  precipitates 
are  produced  in  the  regular  course  of  analysis  when  the 
solution  contains  the  corresponding  salts  of  tin.  They  are 
soluble  in  yellow  ammonium  sulphide. 

141.  Tests  for  Tin.  —  1.  Metallic  tin  is  recognised  by  its 
lustre  and  by  the  emission  of  a  crackling  sound  when  bent 
or  bitten. 

2.  Any  solid  containing  tin,  or  metallic  tin  itself,  when 
heated  on  charcoal  in  the  oxidizing  flame,  gives  a  coating 


122  BISMUTH. 

around  the  assay  which  is  pale  yellow  while  hot  and  white 
when  cold. 

3.  A  solid  may  be  tested  by  dissolving  in  hydrochloric 
acid  and  then  adding  a  solution  of  mercuric  chloride.  At 
first  a  white  precipitate,  Hg2Cl2,  is  obtained.  This  soon 
turns  black,  metallic  mercury  being  set  free.  See  Art. 
130,  3. 

BISMUTH. 

142.  Occurrence  and  Preparation.  —  Bismuth  usually  oc- 
curs native,  but  it  is  always  contaminated  with  a  small 
percentage  of  other  metals.      Its  chief  ores  are  bismuth 
ochre,  Bi2O3,  and  bismuthite,  Bi2S3. 

EXP.  89.  Make  a  pellet  of  any  bismuth  compound  with 
sodium  carbonate  and  a  drop  of  water.  Heat  this  pellet  on 
charcoal  in  the  reducing  flame,  and  test  the  bead  obtained,  as 
usual.  Then  heat  the  bead  in  the  oxidizing  flame,  and  note 
the  coating,  Bi203,  which  is  formed  around  the  assay. 

Bismuth  can  be  partially  obtained  by  heating  its  ores ; 
but  the  extraction  is  made  complete  by  first  roasting  the 
ore,  after  which  it  is  fused  with  iron  slag  and  charcoal. 
The  crude  bismuth  thus  obtained  is  purified  by  fusing  it 
at  the  lowest  possible  temperature  on  an  inclined  plane ; 
the  molten  metal  runs  slowly  down  the  plane,  while  the 
impurities  remain  behind. 

143.  Properties  and  Compounds  of  Bismuth.  —  Bismuth  is  a 
hard,  brittle  metal  of  a  grayish  white  color,  with  a  distinct 
tinge  of  red.     It  oxidizes  slowly  in  the  atmosphere.     It  is 
not  employed  in  a  pure  state,  but  is  chiefly  used  in  making 
alloys  and  in  making  pharmaceutical  preparations.     Bis- 
muth alloys  expand  while  cooling.     The  fusible  metals 


BISMUTH.  123 

used  in  stereotyping  and  in  electrotyping  are  alloys  of  bis- 
muth with  lead,  tin,  and  cadmium. 

Bismuth  forms  two  series  of  salts  similar  to  antimony. 
In  one  class  bismuth  acts  as  a  triad;  in  the  other,  BiO 
appears,  acting  as  a  monad.  The  salts  of  the  latter  are 
called  bismuthyl  salts.  Bi(NO3)3  and  BiONO3  are  exam- 
ples. 

Nitric  acid  is  a  good  solvent  for  bismuth  when  a  work- 
ing compound  is  desired.  But  the  solution  in  water  must 
be  acid,  as  water  changes  bismuth  nitrate  into  bismuthyl 
nitrate,  an  insoluble  compound. 

Some  compounds  of  bismuth  follow :  — 

(0)  Of  the  Bismuth  Oxides,  Bi2O3  is  the  principal  one. 
It  is  used  as  a  pigment. 

(6)  Bismuth  Nitrate,  Bi(NO3)3-f  3H2O,  is  obtained  by 
the  action  of  the  metal  on  nitric  acid.  Bismuthyl  Nitrate, 
BiONO3H2O,  is  the  so-called  Subnitrate  of  Bismuth  of  the 
pharmacopoeia.  It  is  obtained  by  adding  water  to  the 
nitrate.  It  is  used  in  medicine  as  a  remedy  for  cholera 
and  dysentery.  It  is  also  used  as  a  cosmetic  under  various 
names,  as  Blanc  d'Espagne  and  Blanc  de  Fard.  It  is 
further  used  in  glazing  porcelain,  to  which  it  imparts  an 
iridescent  surface. 

(<?)  Bismuth  Trisulphide,  Bi2S3,  is  the  black  precipitate 
obtained  in  analysis.  It  is  soluble  in  hot  nitric  acid. 

144.  Tests  for  Bismuth. — 1.  Any  bismuth  compound  when 
heated  with  sodium  carbonate  on  charcoal  gives  a  metallic 
bead.  If  the  bead  be  heated  in  the  oxidizing  flame,  a 
coating  is  obtained  around  the  assay  of  bismuth  trioxide, 
Bi2O3.  This  coating  is  orange-yellow  while  hot,  lemon- 
yellow  when  cold,  and  the  edges  of  the  coating  are  bluish 
white. 


UNIVERSITY 


124  COPPER. 

2.  An  unknown  solution  may  be  tested  as  follows :  — 

(a)  Add  water  to  the  solution.  A  white  precipitate  of 
a  bismuthyl  salt  is  obtained,  provided  the  solution  be  not 
too  acid. 

(&)  Ammonia  gives  a  white  precipitate,  Bi(OH)3. 

(V)  K2Cr2O7  gives  a  yellow  precipitate,  (BiO)2Cr2O7 
which  is  insoluble  in  KOH  —  a  distinction  from  lead. 

(cT)  H2S  gives  a  black  precipitate,  Bi2S3,  soluble  in  hot 
nitric  acid. 

COPPER. 

145.  Occurrence  and  Preparation.  —  Copper  occurs  native 
in  large  quantities.  The  most  plentiful  deposits  are  found 
in  Upper  Michigan,  where  it  is  found  in  sheets  or  veins 
intersecting  red  sandstone  and  trap  rocks ;  but  the  largest 
deposits  are  found  as  granular  masses  mixed  through  a 
rocky  matrix.  Masses  of  pure  copper  weighing  tons  have 
been  found. 

The  argentiferous  ores  of  the  Rocky  Mountains  also 
furnish  a  large  amount  of  copper.  Many  other  localities 
afford  copper,  both  free  and  combined. 

The  commercial  preparation  of  copper  is  a  simple  pro- 
cess when  applied  to  the  native  copper  deposits.  The  pure 
copper  is  simply  freed  from  all  impurities  by  smelting. 

EXP.  90.  Place  a  bright  steel  nail  in  a  solution  of  copper 
sulphate,  CuS04.  Note  the  coating  of  copper. 

The  reduction  of  copper  from  its  solutions  has  many 
familiar  illustrations.  The  plates  of  gravity-batteries  soon 
become  covered  with  a  deposit  of  metallic  copper.  In  elec- 
trotyping,  copper  is  deposited  upon  a  wax  mould  of  the 
type ;  and  many  metals,  when  placed  in  a  copper  solution, 
receive  a  coating  of  copper. 


CADMIUM.  125 

146.  Properties  and  Compounds  of  Copper.  —  Copper  is  a 
tough,  malleable  metal  which  soon  tarnishes  in  moist  air 
containing  carbon  dioxide.     It  is  a  good  conductor  of  elec- 
tricity, and  enormous  quantities  of  copper  are  used  in  mak- 
ing wire  for  electrical  purposes.     Sheet  copper  is  largely 
used  in  making  household  utensils  and  in  sheathing  ships 
for  ocean  navigation. 

Copper  was  used  by  prehistoric  man  for  making  all 
kinds  of  weapons  and  utensils  which  his  rude  ingenuity 
could  devise. 

There  are  two  series  of  copper  salts  "and  no  copper  acids. 
Copper  sulphate  affords  a  good  working  solution  in  the 
laboratory.  Copper  sulphate,  or  blue  vitriol,  as  it  is  often 
called,  is  the  principal  compound  of  copper  to  be  found  in 
the  market.  The  formula  of  the  crystals  is 

CuS04  +  5H20. 

147.  Tests  for  Copper.  —  1.  A  solid  is  to  be  dissolved  in 
nitric  acid  and  the  solution  tested  by  2. 

2.  A  solution  of  copper  is  tested  by  adding  ammonia. 
When  the  amount  of  the  ammonia  is  short  of  an  excess,  a 
white  precipitate  is  formed;  but  as  soon  as  an  excess  of 
ammonia  is  added,  the  precipitate  dissolves,  and  a  splendid 
blue  solution  is  formed. 

3.  H2S  gives  a  black  precipitate,  which  may  be  dissolved 
in  nitric  acid  and  tested  by  2. 

CADMIUM. 

148.  Occurrence  and  Preparation.  —  Cadmium  is  a  some- 
what rare  metal  occurring  associated  with  zinc.     In  the 
zinc  furnaces  cadmium  is  oxidized  to  CdO,  a  vapor  which 
is  condensed  and  afterward  reduced  by  heating  in  closed 


126  CADMIUM. 

tubes  with  charcoal.  The  uses  of  the  free  metal  are  very 
limited. 

Cadmium  is  a  tin-white  metal  which  slowly  oxidizes  in 
the  air,  which  imparts  to  the  metal  a  yellowish  cast. 
When  strongly  heated  in  the  air,  it  burns,  forming  the 
oxide,  CdO. 

Cadmium  iodide,  CdI2,  is  used  in  photography.  The 
sulphide,  CdS,  is  obtained  in  analysis. 

149.  Tests  for  Cadmium.  —  1.  A  solid  containing  cadmium 
when  heated   on  charcoal   in    the   oxidizing  flame  yields 
brownish  yellow  fumes  of  CdO.     The  coating  around  the 
assay  is  of  the  same  color. 

2.  A  solution  containing  cadmium  gives  the  yellow  pre- 
cipitate, CdS,  with  H2S. 

150.  Separation  and  Identification  of  the  Second  Group  Met- 
als.—  After  removing  the  first  group  metals  with  hydro- 
chloric acid,  hydrogen  sulphide,  H2S,  is  passed  for  a  long 
time  through  the  acid  filtrate.     If  any  or  all  of  the  second 
group  metals  are  present  in  the  filtrate,  they  are  precipi- 
tated as  sulphides.     First  these  sulphides  are  filtered  out, 
and  then  they  must  be  washed  with  much  water,  as  they 
lie  on  the  filter-paper.     Then  make  a  hole  in  the  point  of 
the  paper,  and  by  means  of  a  stream  of  water  from  a  blow- 
bottle,  wash  the  precipitate  through  into  an  evaporating- 
dish.     Now  add  yellow  ammonium  sulphide  and  digest  for 
some  time.     The  sulphides  of  arsenic,  antimony,  and  tin 
will  dissolve,  while  the  sulphides  of  bismuth,  copper,  and 
cadmium  are  unaltered.     Filter  the  contents  of  the  evapo- 
rating-dish.     Treat  the  filtrate  by  I. ;  treat  the  residue  on 
the  filter-paper  by  II. 


CADMIUM.  127 

I. 

ARSENIC,    ANTIMONY,    AND   TIN. 

To  the  filtrate  add  hydrochloric  acid.  The  sulphides  of 
arsenic,  antimony,  and  tin  are  re-precipitated.  Filter  and 
wash  the  precipitate,  and  then  wash  it  through  into  an 
evapora ting-dish.  Add  concentrated  hydrochloric  acid  and 
boil  as  long  as  the  odor  of  hydrogen  sulphide  can  be 
detected.  The  sulphide  of  arsenic  remains  undissolved, 
while  those  of  tin  and  antimony  are  dissolved.  Filter  the 
contents  of  the  evaporating-dish,  and  test  the  residue  on 
the  filter-paper  for  arsenic  by  Art.  135,  1  and  3. 

To  the  nitrate  add  a  few  pieces  of  metallic  zinc.  Anti- 
mony and  tin  are  both  reduced  to  the  metallic  state.  Pour 
off  the  solution,  and  wash  the  two  metals  in  water  by  decan- 
tation.  Add  hydrochloric  acid  to  the  metals.  Only  the 
tin  is  dissolved.  Filter,  and  test  the  filtrate  for  tin  by  Art. 
141,  3. 

Metallic  antimony  remains  on  the  filter-paper.  Test  by 
Art.  138,  1.  Also  dissolve  in  hot  nitro-hydrochloric  acid, 
and  test  by  Art.  138,  2. 

II. 

BISMUTH,    COPPER,    AND   CADMIUM. 

Add  hot  nitric  acid  to  the  sulphides  of  these  metals  as 
they  are  lying  on  the  filter-paper.  The  sulphides  all  dis- 
solve ; 1  save  the  solution  as  it  runs  through,  and  evaporate 

1  If  a  black  residue  remains  after  treating  with  nitric  acid,  it  is 
probably  mercury  in  the  mercuric  condition.  Therefore  dissolve  this 
black  residue  in  nitro-hydrochloric  acid,  expel  the  excess  of  acid,  and  add 
SnCl2.  See  Art.  130,  3. 


128  GOLD    AND   PLATINUM. 

it  to  dry  ness  to  expel  the  excess  of  acid.     Dissolve  the 
residue  in  water  and  then  add  an  excess  of  ammonia.1 

1.  The  bismuth  is  precipitated  as  bismuth  hydroxide, 
Bi(OH)3;  copper  and  cadmium  remain  in  solution.     Fil- 
ter out  the  Bi(OH)3,  and  save  the  nitrate  to  test  by  2;  dis- 
solve the  Bi(OH)3  in  a  little  hydrochloric  acid  and  expel 
any  excess  of  acid ;  a  little  water  will  now  give  a  white 
precipitate  of  bismuthyl  chloride,  BiOCl.     This  is  suffi- 
cient to  identify  the  bismuth. 

2.  When  ammonia  was  added,  if  copper  salts  were  pres- 
ent, the  solution  turned  blue.     No  further  identification  of 
copper  is  necessary.     In  order  to  determine  if  cadmium  be 
present,  add  to  the  blue  solution  a  solution  of  potassium 
cyanide,  KCN,  until  the  blue  color  is  destroyed.     Now 
pass  hydrogen  sulphide  through  the  solution.    If  cadmium 
be  present,  it  will  be  precipitated  as  the  yellow  sulphide, 
CdS.     Test  this  sulphide  by  Art.  149,  1. 

GOLD   AND   PLATINUM. 

151.  Gold.  —  Gold  always  occurs  native.  It  is  widely 
distributed  in  the  older  sedimentary  and  igneous  rocks. 
Rivers  running  through  these  rocks  wash  down  fine  parti- 
cles of  gold  and  sand.  From  these  sands  the  miner  sepa- 
rates the  gold  by  washing  in  shallow  pans  or  cradles. 
Lumps  or  nuggets  of  gold  have  been  found,  of  great  value, 
especially  in  California  and  in  Australia. 

1  If  lead  was  found  in  the  first  group,  it  will  almost  be  sure  to  ap- 
pear in  the  solution  containing  bismuth,  copper,  and  cadmium.  There- 
fore in  such  a  case,  before  adding  ammonia,  try  a  small  portion  of  the 
solution  with  sulphuric  acid.  If  a  precipitate  appears,  add  the  acid  to  the 
whole  solution,  and  thus  precipitate  the  lead  as  PbSO4.  Filter  out  the 
precipitate,  and  then  to  the  filtrate  add  an  excess  of  ammonia,  etc. 


GOLD   AND   PLATINUM.  129 

On  the  Pacific  coast  of  the  United  States  man  has  imi- 
tated nature  by  directing  powerful  streams  of  water  against 
the  sides  of  hills  from  which  some  of  the  rivers  obtain  their 
supply  of  gold-dust.  The  detritus  washed  down  is  con- 
veyed through  sluices,  in  the  bottom  of  which  are  placed 
pockets  containing  mercury  to  catch  the  gold  as  it  comes 
along.  The  gold  is  separated  from  the  mercury  by  heat. 

Gold  occurs  also  in  quartz  rock.  In  such  cases  the  rock 
is  crushed  to  dust,  and  the  gold  is  recovered  by  amalga- 
mation. 

Gold  has  been  known  and  prized  as  a  precious  metal 
from  the  earliest  times.  It  is  usually  necessary  to  alloy 
the  gold  with  a  harder  metal  before  it  is  made  into  coins 
and  je weliy.  Silver  and  copper  are  employed  to  give  the 
requisite  amount  of  hardness  to  gold  employed  for  these 
purposes. 

152.  Platinum.  —  Platinum  is  a  silver-white  metal  of 
great  use  to  the  chemist,  who  uses  it  in  the  form  of  wire, 
foil,  crucibles,  and  evaporating-dishes. 

Platinum  is  infusible  at  temperatures  usually  employed 
in  the  laboratory,  but  it  can  be  fused  in  the  oxyhydrogen 
flame.  It  does  not  tarnish  in  the  air,  and  is  insoluble  in  all 
acids  except  iiitro-hydrochloric  acid.  It  is  also  insoluble 
in  the  alkalies. 

Platinum,  like  gold,  always  occurs  native.  It  is  obtained 
free  from  other  metals  of  a  kindred  nature  which  always 
accompany  it,  in  the  .wet  way.  The  platinum-bearing 
compounds  are  dissolved  in  aqua  regia,  when  platinum 
and  the  accompanying  metals  are  changed  into  chlorides. 
Ammonium  chloride  is  next  added  to  the  solution,  when 
the  platinum  is  precipitated  as  a  double  chloride  of  plati- 
num and  ammonium,  (NH4)2PtCl6.  This  precipitate,  when 


130  EXERCISES. 

heated,  yields  spongy  platinum.  Finally,  the  platinum  is 
brought  into  a  coherent  condition  by  heating  it  in  lime 
crucibles  in  the  oxy hydrogen  flame. 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  Compute  the  atomic  heat  for  each  of  the  second  group  metals. 

2.  Write  a  list  of  the   salts  formed  by  tin,   copper,  bismuth,    and 
cadmium. 

3.  Determine  by  experiment  if  each  of  the  second  group  metals  is 
reduced  from  a  solution  of  its  salts  by  metallic  zinc. 

4.  Write  the  reaction  for  each  of  the  following  metals  with  nitric  acid  : 
copper,  bismuth,  and  cadmium. 

5.  Select  some  soluble  salt  for  each  of  the  second  group  metals,  and 
then  write  the  reaction  between  the  salt  selected  and  hydrogen  sulphide. 


CHAPTER  XII. 

THE  THIRD  GROUP  METALS. 

DATA  FOR  COMPUTATIONS.  —  IRON  :  Symbol,  Fe",  Fe/*  ;  Atomic  Weight, 
56 ;  Specific  Heat,  0.1140  ;  Melting-point,  a  white  heat ;  Specific  Grav- 
ity, 7.86.  — CHROMIUM:  Symbol,  Cr"' ;  Atomic  Weight,  52;  Specific 
Heat,  0.09975  ;  Melting-point,  higher  than  the  temperature  of  the  oxy- 
hydrogen  flame  ;  Specific  Gravity,  6.50.  —  ALUMINUM  :  Symbol,  Al'"  ; 
Atomic  Weight,  27 ;  Specific  Heat,  0.2140 ;  Melting-point,  700°  ;  Spe- 
cific Gravity,  2.60.  —  NICKEL  :  Symbol,  Xi"  ;  Atomic  Weight,  58; 
Specific  Heat,  0.1080;  Melting-point,  nearly  a  white  heat;  Specific 
Gravity,  8.90.  —  COBALT  :  Symbol,  Co";  Atomic  Weight,  59  ;  Specific 
Heat,  0.10674;  Melting-point,  a  white  heat;  Specific  Gravity,.  8. 5  to 
8.7.  —  MANGANESE  :  Symbol,  Mn"  ;  Atomic  Weight,  55  ;  Specific  Heat, 
0.1217  ;  Melting-point,  a  white  heat ;  Specific  Gravity,  8.03.  —  ZINC  : 
Symbol,  Zn"  ;  Atomic  Weight,  65  ;  Specific  Heat,  0.0955  ;  Melting- 
point,  423°  ;  Specific  Gravity,  7.15. 

153.  The  Third  Group  Metals  are  precipitated  from  the 
filtrate  obtained  when  the  second  group  metals  are  filtered 
out.  This  filtrate,  as  previously  mentioned,  needs  a  little 
preliminary  treatment  before  the  reagents  are  applied. 
Iron  must  always  be  present  in  the  ferric  condition.  The 
hydrogen  sulphide  employed  to  throw  down  the  second 
group  metals  has  reduced  any  iron  compounds  to  the  fer- 
rous condition.  Moreover,  it  has  reduced  chromium,  if 
present  as  an  acid,  to  chromium  as  a  base,  which  leaves  the 
chromium  in  a  proper  condition  for  the  application  of  the 
necessary  reagents.  In  deference  to  any  iron  that  may  be 
present  it  is  necessary  to  boil  the  filtrate  until  all  hydro- 
gen sulphide  be  removed,  after  which  nitric  acid  is  added, 

131 


132  IRON. 

and  the  solution  is  boiled  again  for  a  short  time.  The 
nitric  acid  added  oxidizes  iron,  if  present,  to  the  ferric 
state,  and  the  solution  is  now  ready  for  the  application  of 
the  needed  reagents. 

Accordingly  ammonia  and  ammonium  chloride  are  imme- 
diately added,  and  thus  are  iron,  chromium,  and  aluminum 
precipitated  as  the  hydroxides,  Fe2(OH)6,  Cr2(OH)6,  and 
A12(OH)6.  These  precipitates  are  now  removed  by  filtra- 
tion and  to  the  filtrate,  ammonium  sulphide,  (NH4)2S,  is 
added.  Thus  are  obtained  as  precipitates  the  sulphides, 
NiS,  CoS,  MnS,  and  ZnS.  This  completes  the  precipita- 
tion of  the  third  group  metals. 

IRON. 

154.  Occurrence  and  Preparation.  —  Metallic  iron  occurs 
only  in  insignificant  quantities.  Meteorites  usually  con- 
tain metallic  iron  together  with  other  metals.  But  the 
compounds  of  iron  are  distributed  almost  everywhere. 
The  color  of  vegetation  is  due  to  iron  compounds,  and 
nearly  every  soil  contains  some  form  of  combined  iron. 
Its  ores  are  widely  distributed,  but  the  localities  are  some- 
what restricted  in  extent.  Iron  pyrites,  FeS2,  or  fool's 
gold,  is  a  well-known  mineral  on  account  of  its  yellow 
lustre  resembling  gold. 

Of  the  ores  employed  in  the  United  States  for  preparing 
commercial  iron,  the  most  important  is  haematite,  Fe2O3. 
This  ore  assumes  a  variety  of  forms.  The  amorphous  form 
resembles  iron  rust,  while  the  micaceous  ore  occurs  in  glit- 
tering scales.  Bog  ore,  Fe2O3  +  Fe2(OH)6,  also  called 
brown  haematite,  is  the  ore  chiefly  employed  in  Ger- 
many and  France.  Argillaceous  ore,  or  clay  iron-stone,  is 
employed  in  England.  Magnetite  or  lodestone,  Fe3O4,  is 


IRON. 


133 


interesting   on   account    of    its   constituting    the   natural 
magnet. 

The  reduction  of  iron  from  its  ores  is  one  of  the  most 
important  industries  of  the  age,  and  the  furnaces  and  the 
machinery  required  are  expensive.  The 
form  of  the  modern  blast-furnace  is 
shown  in  Fig.  29.  It  is  from  fifty  to 
ninety  feet  high,  and  from  fourteen  to 
twenty  feet  broad  in  its  widest  part.  It 
is  constructed  of  masonry,  lined  with 
fire-brick,  and  enclosed  down  to  the 
point  A  in  riveted  iron  boiler-plates. 
Before  the  furnace  goes  into  blast,  the 
masonry  does  not  extend  below  A,  but 
the  stack  is  supported  on  strong  iron 
pillars  resting  on  a  solid  foundation. 
These  pillars  are  not  shown  in  the  cut. 
The  hearth,  H,  consists  of  fire-clay,  and 
it  is  here  that  the  molten  iron  collects.  There  are  two 
openings  in  this  hearth :  the  lower  one  for  drawing  off  the 
cast  iron,  and  the  upper  one  for  removing  the  glassy  slag 
obtained  during  the  reduction  of  the  ore.  The  top  of  the 
stack  D  is  funnel-shaped,  and  is  closed  by  an  inverted 
cone,  E,  which  can  be  raised  or  lowered  while  charging  the 
furnace. 

When  the  furnace  is  about  to  go  into  blast,  the  spaces  H 
and  B  are  filled  with  cord-wood,  after  which  the  whole  por- 
tion below  A  is  enclosed  by  masonry.  A  number  of  blow- 
pipes, or  "  tuyeres,"  are  built  into  the  masonry.  Through 
these,  powerful  blasts  of  air  are  maintained  when  the  fur- 
nace is  in  operation. 

In  starting  the  furnace,  the  wood  is  first  ignited  and  the 
blast  is  turned  on.  Then  stone-coal  is  introduced  at  the 


FIG.  29. 


134  IKON. 

top  of  the  stack.  When  the  stack  has  become  thoroughly 
heated,  finely  crushed  ore,  stone-coal,  and  limestone  are 
regularly  added  at  the  top  of  the  stack.  Barring  accidents, 
a  furnace  runs  night  and  day,  shutting  down  but  once  or 
twice  a  year  to  repair  the  stack. 

The  chemical  changes  which  occur  in  the  stack  are  not 
well  understood,  but  the  products  obtained  are  cast  iron,  a 
glassy  slag,  carbon  dioxide,  carbon  monoxide,  hydrogen,  cy- 
anogen, graphite,  and  perhaps  certain  hydrocarbons.  These 
gases,  some  of  which  are  inflammable,  are  not  wasted,  but 
are  led  through  the  pipe  G  to  boilers  which  furnish  steam 
to  the  engines  that  run  the  machinery  employed. 

The  iron  obtained  from  the  blast-furnace  is  not  pure 
iron.  It  is  called  cast  iron,  and  contains  carbon,  silicon, 
traces  of  arsenic,  sulphur,  and  phosphorus,  and  small  quan- 
tities of  various  metals. 

From  this  cast  iron,  wrought  iron  is  obtained  by  the 
processes  termed  "  refining  "  and  "  puddling."  In  these 
operations  the  impurities  are  burned  out  and  the  metal  is 
hammered  into  coherence,  after  which  it  is 
rolled  into  bars  and  sent  to  market. 

Steel  is  now  obtained  by  the  Bessemer 
process  from  cast  iron.  The  molten  cast 
iron  is  run  into  an  egg-shaped  vessel,  called 
a  "  converter  "  (Fig.  30),  and  a  blast  of  air 
is  driven  up  through  the  molten  metal. 
30  The  impurities  are  thus  burned  out,  leaving 
nearly  pure  iron.  Steel  stands  about  mid- 
way in  its  content  of  carbon  and  silicon  between  cast  and 
wrought  iron.  In  order  to  furnish  the  proper  amounts 
of  these  two  substances,  a  pure  variety  of  cast  iron,  called 
"  spiegel  iron,"  is  now  added  to  the  pure  iron,  thus  con- 
verting the  whole  into  steel, 


IRON.  135 

155.  Properties  and  Compounds  of  Iron.  —  Iron  is  a  nearly 
silver-white  metal  that  rusts  quickly  when  exposed  to 
damp  air,  thus  receiving  a  coating  of  ferric  oxide  and  fer- 
ric hydroxide.  It  is  a  tenacious  metal  which  possesses  the 
property  of  softening  before  it  melts,  thus  allowing  dif- 
ferent pieces  to  be  welded. 

The  uses  of  iron  are  so  many  and  so  important  that  this 
age  has  been  well  termed  the  iron  age. 

Iron  forms  two  series  of  salts,  —  the  ferrous  and  the 
ferric.  These  salts  are  exemplified  by  the  two  chlorides, 
ferrous  chloride,  FeCL,  and  ferric  chloride,  Fe2Cl6.  It  will 
be  noticed  that  in  the  ferrous  compounds  iron  is  bivalent, 
while  in 'the  ferric  state  two  atoms  are  hexavalent.  As  in 
the  mercurous  compounds,  the  ferric  salts  are  written  with 
an  even  number  of  atoms. 

Iron  dissolves  in  almost  any  of  the  acids,  and  any  of  the 
salts  make  good  working  solutions.  Some  of  the  more 
important  compounds  follow :  - 

(a)  Ferric  Hydroxide,  Fe2(OH)6,  is  obtained  by  adding 
ammonia  to  almost  any  ferric  salt.  It  is  the  precipitate 
obtained  in  analysis. 

(5)  Ferric  Chloride,  Fe2Cl6,  is  obtained  when  iron  wire 
is  dissolved  in  hydrochloric  acid,  after  which  the  solution 
is  thoroughly  saturated  with  chlorine  gas.  It  is  used  in 
medicine,  and  in  the  laboratory  it  is  an  important  reagent. 

(c)  Ferrous   Sulphate,   FeSO4  +  7  H.2O,  is   often  called 
copperas  and  green  vitriol.     It  may  be  obtained  by  dis- 
solving iron  or  ferrous  sulphide  in  sulphuric  acid.     The 
commercial  article  is  often  prepared  by  roasting  iron  py- 
rites at  a  moderate  heat.     It  is  used  as  a  disinfectant,  as  a 
reagent,  and  in  preparing  fuming  sulphuric  acid.     It  is 
also  used  in  dyeing. 

(d)  Ferrous  Sulphide,  FeS,  is  made  by  stirring  molten 


136 


IRON. 


sulphur  with  a  white-hot  wrought-iron  rod.  It  is  used  in 
the  laboratory  as  a  source  of  hydrogen  sulphide. 

(e)  Potassium  Ferrocyanide,  K4Fe(CN)6,  is  obtained  by 
heating  scrap  iron  in  closed  iron  retorts  with  potash  and 
animal  matter,  such  as  hoofs,  horns,  etc. 

Tins  compound  serves  as  the  starting-point  in  the  man- 
ufacture of  all  of  the  cyanogen  compounds.  It  is  used 
in  the  manufacture  of  Prussian  blue,  Fe7(CN)18.  This 
pigment  is  obtained  when  ferric  chloride  is  added  to  po- 
tassium ferrocyanide.  In  the  laboratory,  potassium  ferro- 
cyanide  is  used  as  a  reagent  for  the  detection  of  iron.  The 
ferricyanide  is  obtained  by  oxidizing  the  ferrocyanide  with 
chlorine.  Its  formula  is  K3Fe(CN)6. 

156.  Tests  for  Iron.  —  1.  Solids  are  first  brought  into 
solution  by  using  water  as  a  solvent.  If  water  will  not 
dissolve  the  solid,  an  acid  is  used.  The  solution  is  then 
tested  by  2. 

2.  For  testing  a  solution  for  iron,  the  reagents  potas- 
sium sulphocyanide,  RONS,  potassium  ferrocyanide, 
K4Fe(OX)6,  and  potassium  ferricyanide,  K3Fe(CN)6,  arc 
used.  Ferrous  and  ferric  salts  act  differently,  as  shown 
by  the  following  table  :  — 


REAGENT. 

FERRIC  SALT. 

FERROUS  SALT. 

KCNS 

K4Fe(CN)6 
K3Fe(CX)6 

Red  sol.    Fea(CNS)0 
Deep  blue  prec.    Fe4[Fe(CN)G]3 
No  prec.     Reddish  brown  sol. 

No  change. 
Pale  blue  prec.     K2Fe,  Fe(CN)R 
Deep  blue  prec.    Fe3[Fe(CN)6]2 

3.  Ferrocyanic,  ferricyanic,  and  sulphocyanic  acids  may 
be  detected  by  employing  as  reagents  ferric  chloride,  Fe2Cl6, 
and  ferrous  sulphate,  FeSO4,  by  means  of  the  table  given 
in  2. 


CHROMIUM.  137 


CHROMIUM. 

157.  Occurrence  and  Preparation.  —  Chromium  is  a  rare 
metal  not  employed  in  the  arts.     Its  chief  ores  are  crocoi- 
site,  or   chrome  yellow,  PbCrO4,  and  chrome  iron-stone, 
Cr2O3(FeO).     Small  quantities  of  the  metal  are  obtained 
by  mixing  its  oxide  with  sugar,  after  which  the  mixture  is 
strongly  heated  in  lime  crucibles. 

158.  Properties  and  Compounds.  —  Chromium  imparts  a 
superior  hardness  to  steel.     Its  compounds  are  numerous 
and  important.     It  acts  as  a  base,  and  is  also  an  acid-form- 
ing  element.      Potassium   bichromate    and   chrome   alum 
answer   well    for   working    purposes   in    the    laboratory. 
These  compounds  and  a  few  others  are  noticed. 

(a)  Chromic  Oxide,  Cr2O3,  is  obtained  by  fusing  potas- 
sium bichromate  with  sulphur  or  with  ammonium  chloride, 
after  which  the  fused  mass  is  treated  with  water.     It  is 
used  in  coloring  glass  and  enamel  green.     This  oxide  may 
be  regarded  as  the  anhydride  of  the  hypothetical  chromic 
acid,  H2CrO4.     Chromic  hydroxide,  Cr.2(OH)6,  is  obtained 
when  ammonia  is  added  to  a  solution  containing  chromium 
as  a  base. 

(b)  G-uignet's  G-reen,  or  chrome  green,  Cr2O(OH)4,  is 
used  as  a  pigment.     It  is  obtained  by  fusing  potassium 
bichromate  and  crystallized  boric  acid  mixed  in  propor- 
tions corresponding  to  their  molecular  weights. 

(<?)  Chrome  Alum,  or  potassium  chromium  sulphate, 
K2Cr2(SO4)4  +  24  H2O,  is  used  in  dyeing,  tanning,  and  in 
calico-printing.  It  is  obtained  as  a  by-product  in  the  man- 
ufacture of  alizarine. 

(d)   Potassium  Bichromate,   K2Cr2O7,   is  obtained  from 


138  ALUMINUM. 

» 

chrome  iron  ore.  The  ore  is  first  roasted  to  oxidize  it,  and 
then  it  is  fused  with  lime  and  potassium  carbonate ;  then 
the  fused  mass  is  leached  with  as  little  water  as  possible, 
and  the  filtrate  is  treated  with  sulphuric  acid.  This  salt 
is  extensively  used  in  batteries,  in  dyeing,  in  preparing  the 
pigment,  chrome  yellow,  PbCrO4,  and  other  compounds, 
and  as  a  reagent. 

159.  Tests  for  Chromium. — 1.  A  solid  is  fused  on  char- 
coal with  potassium  nitrate  and  sodium  carbonate  in  order 
to  oxidize  any  chromium  present  to  a  chromate.     Now  dis- 
solve the  yellow  mass  obtained  in  water,  and  add  acetic 
acid  to  an  acid  reaction.     Finally,  add  lead  acetate,  when  a 
yellow  precipitate,  PbCrO4,  will  be  obtained. 

2.  A  chromate  or  a  bichromate  in  solution  gives  with  — 
Hydrogen  sulphide,  H2S,  a  green  solution ; 
Lead  acetate,  Pb(C2H3O2)2,  a  yellow  precipitate,  PbCrO4; 
Silver   nitrate,    AgNO3,   a    brownish   red    precipitate, 
AgCrO4. 

ALUMINUM. 

160.  Occurrence    and    Preparation.  —  Although   metallic 
aluminum  never  occurs  free,  in  compounds  it  occurs  in 
enormous  quantities.     It  ranks  next  to  oxygen  and  silicon 
in  its  abundance.     It  is  the  basis  of  clayey  soils,  and  it 
occurs  as  feldspar,  K2Al2Si6O16,   in  many  different  kinds  of 
rocks.     Kaolin,  or  porcelain  clay  and  china  clay,  is  simply 
weathered  feldspar. 

Aluminum  trioxide,  A12O3,  is  well  known  as  corundum  or 
emery.  Crystallized  forms  of  this  substance  are  known  as 
the  jewels  sapphire,  ruby,  oriental  emerald,  oriental  topaz, 
and  oriental  amethyst.  Other  gems  also  have  aluminum 
as  a  base :  thus,  turquoise  is  a  phosphate  of  aluminum 


ALUMINUM.  139 

colored   with   copper ;    topaz   and    beryl  are   silicates   of 
aluminum. 

Aluminum  can  only  be  reduced  from  its  ores  by  expen- 
sive processes.  Of  late  the  metal  has  been  prepared  by 
reducing  the  trioxide  mixed  with  carbon  in  lime  crucibles 
by  means  of  electricity. 

161.  Properties  and  Compounds.  —  Aluminum  is  a  white, 
malleable  metal  that  does  not  tarnish  under  ordinary  cir- 
cumstances. Its  physical  properties  fit  it  for  many  uses 
that  the  great  cost  of  its  production  alone  forbids.  It  is 
chiefly  employed  at  present  in  making  philosophical  instru- 
ments. Aluminum  bronze  is  now  being  much  used  for 
making  ornamental  household  fixtures. 

Any  one  of  the  alums  affords  a  good  working  solution. 
Several  compounds  that  have  not  been  noted  follow :  — 

(a)  Aluminum  Hydroxide,  A12(OH)6,  is  obtained  when 
ammonia  is  added  to  any  soluble  aluminum  salt.  It  is  the 
precipitate  obtained  in  analysis. 

(li)  Aluminum  Sulphate,  A12(SO4)3,  is  obtained  by  act- 
ing on  roasted  kaolin  with  sulphuric  acid.  This  is  used 
in  immense  quantities  as  a  mordant  and  for  weighting 
paper. 

(e)  The  alums  are  an  interesting  class  of  compounds. 
The  formula  for  potassium  alum  will  serve  as  a  type  for 
all  the  others,  K2A12(SO4)4  +  24  H2O.  In  place  of  the 
potassium,  other  metals  may  be  substituted ;  thus  we  have 
silver  alum,  ammonium  alum,  chromium  alum,  etc. 

(d)  Sodium  Aluminate  is  prepared  by  fusing  bauxite, 
Al2Fe2O8H4,  with  sodium  sulphate  and  carbon.  It  is  used 
as  a  mordant  in  dyeing  and  in  calico-printing,  for  prepar- 
ing colored  lakes  and  for  sizing  paper. 


140  NICKEL. 

162.  Tests  for  Aluminum.  —  1.  A  solution  is  tested  by  2. 
A  solid  is  first  fused  on  charcoal  with  sodium  carbonate, 
the  fused  mass  is  dissolved  in  hydrochloric  acid,  and  the 
solution  tested  by  2. 

2.  A  solution  is  tested  as  follows :  — 

(a)  An  excess  of  ammonia  and  ammonium  chloride 
gives  a  white,  gelatinous  precipitate,  A12(OH)6. 

(6)  A  solution  of  sodium  carbonate  gives  the  same 
precipitate. 

(c>)  Disodium  phosphate  gives  a  white  precipitate, 
A12(PO4)2,  soluble  in  potassium  hydroxide,  insoluble  in 
acetic  acid. 

NICKEL. 

163.  Occurrence  and  Preparation.  —  Nickel  never  occurs 
free.     Its  ores  occur  in  connection  with  the  cobalt  ores. 
The  most  important  ore  is  kupfer-nickel,  NiAs.     Metallic 
nickel  is  obtained  mostly  in  the  wet  way.     The  ore  is  first 
roasted,  and  then  dissolved  in  hydrochloric  acid.     This 
solution  usually  contains  the  chlorides  of  other  metals  as 
well  as  nickel  chloride.     These  foreign  metals  are  precipi- 
tated by  the  addition  of  proper  reagents,  leaving  the  nickel 
in  solution,  from  which  it  is  precipitated  by  adding  sodium 
hydroxide.    The  nickel  hydroxide,  Ni(OH)2,  thus  obtained 
is  reduced  by  the  action  of  charcoal  at  high  temperatures. 

164.  Properties  and  Compounds  of  Nickel.  —  Nickel  is  a 
white,  hard  metal,  susceptible  of  a  high  polish  and  scarcely 
tarnishing  in  the  air.     It  is  accordingly  used  for  coinage 
and  for  nickel-plating  other  metals,  especially  iron.     Ger- 
man silver  is  an  alloy  of  copper,  5  parts  ;  nickel,  2  parts  ; 
and  zinc,  2  parts.     Nickel  resembles  iron  in  that  it  can  be 
welded  and  can  be  attracted  by  the  magnet. 


.  S 


COBALT.  S  141 


Nickel  is  soluble  in  dilute  nitric  acid,  yielding  nickel 
nitrate,  Ni(NO3)2,  which  affords  a  good  working  solution. 
The  chloride  and  sulphate  are  also  to  be  had  by  using  the 
proper  acids.  The  salts  of  nickel  are  used  but  little.  The 
sulphide,  NiS,  is  the  black  precipitate  obtained  in  analysis. 
It  is  soluble  in  nitro-hydrochloric  acid. 

165.  Tests  for  Nickel.  —  A  solid  supposed  to  contain  nickel 
is  brought  into  solution  by  means  of  nitro-hydrochloric  acid, 
if  water  will  not  dissolve  it,  and  tested  thus  :  — 

(a)  Ammonia,  when  added  to  a  solution  short  of  an 
excess,  produces  an  apple-green  precipitate,  Ni(OH)2.  An 
excess  of  ammonia  gives  a  blue  solution.  To  this  blue 
solution  add  potassium  hydroxide,  when  the  apple-green 
hydroxide  again  appears. 

(5)  Potassium  hydroxide  added  directly  to  a  nickel 
solution  gives  the  same  apple-green  precipitate. 

2.  Any  nickel  compound  in  a  borax  bead  in  the  oxidiz- 
ing flame  colors  the  bead  brownish  red  while  hot,  yellow 
when  cold.  In  the  reducing  flame  the  bead  becomes  gray, 
metallic  nickel  being  reduced.  Cobalt  interferes  with  this 
test. 

COBALT. 

166.  Occurrence  and  Preparation.  —  Cobalt  does  not  occur 
free,  neither   is  the  metal  used  in  the  arts.     Speiss  co- 
balt, Co(Ni,Fe)As2,  Skutterudite,  CoAs,,  and  cobalt  glance, 
CoFeAs2S2,  are  the  more  important  ores. 

Metallic  cobalt  is  obtained  as  a  gray  metallic  powder  by  ' 
heating  the  oxide  or  chloride  in  an  atmosphere  of  hydrogen. 

The  compounds  of  cobalt  are  used  in  the  arts,  and  they 
are  prepared  directly  from  a  cobalt  ore,  usually  speiss 
cobalt. 


142  MANGANESE. 

167.  Properties  and  Compounds.  —  Cobalt  resembles  iron 
in  color  and  in  being  attracted  by  the  magnet.     The  com- 
pounds of  cobalt  are  useful  as  furnishing  valuable  pig- 
ments.    Some  compounds  follow  :  — 

(a)  Cobalt  Oxide,  CoO,  is  an  article  of  commerce.     It  is 
used  in  coloring  glass  blue  and  in   preparing  the  cobalt 
pigments.     It  may  be  dissolved  in  acids,  forming  salts  of 
the  acids  used.     This  oxide  is  prepared  from  speiss  cobalt. 
The  ore  is  first  roasted,  then  dissolved  in  hydrochloric 
acid,  and  then  the  accompanying  metals  are  precipitated 
by  adding  successively  chlorine,  limestone,  and  hydrogen 
sulphide.     The  oxide  is  now  precipitated  by  the  addition, 
of  bleaching-powder. 

(b)  Cobaltous  Chloride,  CoCl2,  is  used  as  a  sympathetic 
ink.     Its  action  depends  on  the  fact  that  when  moist  the 
salt  is  a  light  pink,  but  when  dry  it  is  violet.     Thus  the 
writing  becomes  visible  when  the  paper  is  warmed. 

(c)  Cobaltous  Nitrate,  Co(NO3)2,  is  used  in  the  labora- 
tory as  a  reagent.     It  can  be  made  by  dissolving  the  metal 
or  the  carbonate  of  the  metal  in  nitric  acid. 

(d)  Cobaltous  Sulphide,  CoS,  is  the  precipitate  obtained 
in  analysis.     It  is  soluble  in  nitro-hydrochloric  acid. 

(e)  Smalt  is  a  silicate  of  cobalt  used  as  a  pigment. 

168.  Tests  for  Cobalt.  —  1.  Any  cobalt  compound  colors 
the  borax  bead  blue.     If  an  excess  of  cobalt  be  present, 
the  bead  may  be  almost  black.     When  powdered,  the  dust 
from  this  bead  is  blue  in  all  cases. 


MANGANESE. 

169.    Occurrence  and  Preparation.  —  Manganese  never  oc- 
curs free  nor  is  it  used  in  the  arts.     Its  chief  ore  is  pyro- 


MANGANESE.  143 

lusite,  MnO2.  It  is  obtained  in  the  metallic  state  by 
fusing  one  of  its  oxides  mixed  with  charcoal  at  a  white 
heat  in  a  closed  crucible  lined  with  graphite. 

170.  Properties  and  Compounds.  —  Manganese  is  a  red- 
dish white  metal,  oxidizing  so  readily  that  it  is  necessary 
to  preserve  it  under  naphtha  or  coal  oil.     Some  of  the  man- 
ganese compounds  follow :  — 

(a)  Manganese  Dioxide,  MnO^  is  the  most  important  of 
the  oxides  of  manganese.  It  is  used  with  hydrochloric 
acid  in  large  quantities  for  generating  chlorine  gas  in  the 
manufacture  of  bleaching-powder.  Its  use  in  the  labora- 
tory has  already  been  exemplified. 

(£>)  Potassium  Permanganate,  K2Mn2O8,  is  used  in  the 
laboratory,  and  an  impure  form  of  sodium  permanganate  is 
used  as  a  disinfecting  fluid  under  the  name  of  Condy's 
Disinfecting  Liquid.  These  salts  may  be  regarded  as 
originating  from  the  acid,  HMnO4,  or  permanganic  acid. 
Manganic  acid,  H2MnO4,  has  not  been  isolated,  but  the 
manganates  are  known. 

(c)  Manganese  Sulphide,  MnS,  is  the  flesh-colored  pre- 
cipitate obtained  in  analysis.  It  is  soluble  in  cold  dilute 
hydrochloric  acid. 

171.  Tests  for  Manganese.  —  1.  Manganese  compounds  in 
the   oxidizing  flame  give  the  borax   bead   a  violet  color 
while  hot,  amethyst-red  when  cold.     In  the  reducing  flame 
the  bead  becomes  colorless. 

2.  A  solid  may  be  fused  on  platinum  or  on  porcelain 
with  sodium  carbonate  and  potassium  nitrate  to  a  bright 
green  mass,  a  manganate.  Dissolve  this  mass  in  nitric 
acid,  and  a  permanganate  is  obtained  in  a  red  solution. 


144  ZINC. 


ZINC. 

172.  Occurrence  and  Preparation. —  Zinc  does  not  occur 
free  in  significant  quantities.     Smithsonite,  ZnCO3,  is  one 
of  the  principal  ores.    Franklinite,  (Zn,Fe)O  +  Fe2O3 ;  zinc 
blende,  ZnS  ;  Willemite,  Zn2SiO4,  and  a  reddish  oxide  owing 
its  color  to  an  oxide  of  manganese,  are  the  principal  ores 
employed  in  the  United  States. 

The  ores  are  first  roasted  and  then  ground  fine  ;  then 
they  are  mixed  with  half  their  weight  of  coal-dust.  Now 
the  mixture  is  placed  in  clay  retorts  and  heated  until  the 
zinc  issues  in  the  form  of  a  vapor,  which  is  condensed 
in  iron  condensers.  Commercial  zinc  as  thus  prepared  is 
seldom  pure,  as  it  contains  small  quantities  of  other 
metals. 

173.  Properties   and   Compounds.  —  Zinc   is   a   malleable, 
ductile,  bluish-white  metal  which  finds  many  uses.     Sheet 
zinc  and  galvanized  iron,  which  is  sheet  iron  coated  with 
zinc,  are  familiar  to  all.     Zinc  alloyed  with  copper  forms 
the  useful  alloy,  brass.     For  batteries  and  in  the  laboratory, 
zinc  is  used  extensively. 

Zinc  dissolves  in  most  of  the  acids  to  form  salts  that  are 
applicable  for  working  purposes.  When  taken  internally 
the  salts  of  zinc  are  poisonous. 

(a)  Zinc  Chloride,  ZnCl2,  is  obtained  when  the  metal  is 
dissolved  in  hydrochloric  acid.  This  salt  is  used  as  a  caus- 
tic in  surgery  ;  and  in  organic  chemistry  it  is  used  for 
removing  the  elements  of  water  from  many  substances. 
It  is  used  in  weighting  cotton  goods,  and  in  tin-shops  as 
a  soldering-fluid. 

(&)  Zinc  White,  ZnO,  is  used  as  a  paint. 


SEPARATION    OF   THE   THIRD   GROUP   METALS.        145 

(c)  Zinc  Sulphate,  or  white  vitriol,  ZnSO4  +  7  H2O,  is 
used  in  medicine  and  in  dyeing. 

(c7)  Zinc  Sulphide,  ZnS,  is  the  white  precipitate  ob- 
tained in  analysis. 

174.  Tests  for  Zinc.  — 1.  Solids,  when  heated  on  charcoal 
in  the  oxidizing  flame,  give  a  coating  around  the  assay, 
yellow  while  hot,  and  white  when  cold.  If  now  the  mass 
and  the  coating  be  moistened  with  cobaltous  nitrate  and 
heated  again,  the  pigment,  Rinnman's  green,  is  obtained. 

2.  A  solution  gives  a  white  precipitate,  ZnS,  when  am- 
monia and  ammonium  sulphide  are  added. 


SEPARATION    OF    THE    THIRD    GROUP    METALS. 

175.  Precipitate  the  iron,  chromium,  and  aluminum  as 
explained  in  Art.  153.  Filter  out  the  precipitate  obtained, 
wash  with  water,  and  then  proceed  by  I. 

Precipitate  the  remaining  metals  of  this  group  by  add- 
ing ammonium  sulphide.  Warm  the  solution  until  the 
sulphides  settle,  then  filter,  wash  the  precipitate,  and 
proceed  by  II. 

I. 

IRON,    CHROMIUM,   AND   ALUMINUM. 

1.  Pierce  the  point  of  the  filter-paper  and  wash  the  pre- 
cipitate through  into  an  evaporating-dish.  Take  a  small 
portion  of  this  precipitate  and  dissolve  it  in  nitric  acid 
with  heat.  Divide  the  solution  thus  obtained  in  two  parts 
and  test  directly  for  iron.  Potassium  sulphocyanide  gives 
a  red  solution ;  potassium  ferrocyanide  gives  a  deep  blue 
precipitate.  (See  Art.  156.)  The  presence  of  chromium 
and  aluminum  will  not  interfere  with  the  tests  for  iron. 


146       SEPARATION   OF  THE  THIRD   GROUP  METALS. 

If  iron  be  found,  test  a  portion  of  the  original  solution  to 
determine  whether  the  iron  in  it  is  in  the  ferrous  or  ferric 
condition. 

2.  For  chromium,  take  a  second  portion  of  the  hydrox- 
ides  in   the   evaporating-dish,    fuse   it   on   charcoal   with 
sodium  carbonate,  etc.,  as  in  Art.  159,  1. 

3.  To  the  remainder  of  the  precipitate  in  the  evapora- 
ting-dish add  potassium  hydroxide  and  boil.     The  alumi- 
num will  dissolve.     Filter,  and  barely  acidify  the  filtrate 
with  hydrochloric  acid;  and  then  add  ammonia  in  excess. 
A  white  precipitate,  A12(OH)6,  identifies  aluminum. 


II. 

NICKEL,   COBALT,   MANGANESE,   AND  ZINC. 

1.  Wash  the  sulphides  of  these  metals  through  into  a 
test-tube  and  add  cold,  dilute  hydrochloric  acid;  shake 
frequently.     The  sulphides  of  nickel  and  cobalt  do  not 
dissolve,  but  manganese  and  zinc  are  brought  into  solution. 
Filter,  and  treat  any  residue  for  nickel  and  cobalt  by  3. 
Treat  the  filtrate  for  manganese  and  zinc  by  2. 

2.  Boil  this  filtrate  to  expel  hydrogen  sulphide,  then  add 
a  decided  excess  of  potassium  hydroxide.     Allow  the  tube 
to  stand,  and  shake  frequently.     Any  manganese  will  be 
precipitated  as  Mn(OH)2.     Filter,  and  test  the  precipitate 
by  Art.  171.     Test  the  filtrate  for  zinc  by  acidifying  with 
acetic  acid  and  adding  ammonium  sulphide.     Any  zinc 
will  give  the  white  precipitate,   ZnS.     Farther  test  this 
precipitate  by  Art.  174,  1. 

3.  This  residue  contains  some  sulphur  obtained  from  the 
sulphides  that  dissolved.     Test  a  portion  of  the  residue  by 
the  borax  bead.     A  blue  bead  identifies  cobalt. 


EXERCISES.  147 

If  both  nickel  and  cobalt  are  present,  it  is  somewhat  dif- 
ficult to  obtain  the  tests  for  nickel,  but  it  may  be  accom- 
plished thus :  dissolve  the  remainder  of  their  sulphides  in 
nitre-hydrochloric  acid,  and  add  to  the  solution  an  excess 
of  potassium  hydroxide.  A  precipitate  may  be  Co(OH)2 
and  Ni(OH)2.  Filter  out  this  precipitate  and  dissolve  it 
in  acetic  acid.  To  this  solution  add  potassium  nitrite, 
KNO2.  Allow  the  tube  to  stand  twenty-four  hours.  Any 
precipitate  will  be  potassium  cobaltic  nitrite ;  this  leaves 
the  nickel  in  solution.  Precipitate  it  by  adding  potassium 
hydroxide,  and  thus  obtain  the  apple-green  hydroxide, 
Ni(OH)2. 

EXERCISES. 

(For  Review  or  Advanced  Course.) 

1.  Compute  the  atomic  heat  for  each  of  the  third  group  metals. 

2.  Determine  by  trial  if  any  of  the  third  group  metals  can  be  reduced 
from  compounds  to  the  metallic  state  by  means  of  the  blow- pipe,  charcoal, 
and  sodium  carbonate. 

3.  Write  the  equations  for  the  separation  of  the  third  group  metals. 

4.  Obtain  a  bit  of  alum  from  the  drug  store,  and  test  it  for  aluminum. 

5.  Dissolve  a  bit  of  iron  in  hydrochloric  acid.    Write  the  reaction.    Do 
you  obtain  ferrous  or  ferric  chloride  ?    Test  by  Art.  156. 


CHAPTER  XIII. 

THE  FOURTH  GROUP  METALS. 

DATA  FOR  COMPUTATIONS.  —  BARIUM:  Symbol,  Ba  '  ;  Atomic  Weight, 
137  ;  Specific  Heat, ;  Melting-point,  higher  than  cast  iron ;  Speci- 
fic Gravity,  3.75.  —  STRONTIUM  :  Symbol,  Sr" ;  Atomic  Weight,  87.2 ; 

Melting-point,  a  red  heat;  Specific  Heat, ;  Specific  Gravity,  2.54. 

—  CALCIUM  :  Symbol,  Ca" ;  Atomic  Weight,  40 ;  Specific  Heat,  0.1804  ; 
Melting-point,  a  red  heat;  Specific  Gravity,  1.57.  —  MAGNESIUM  :  Sym- 
bol, Mg" ;  Atomic  Weight,  24 ;  Specific  Heat,  0.2450 ;  Melting-point, 
750° ;  Specific  Gravity,  1.74. 

176.  The  fourth  group  metals,  often  called  the  "  Metals 
of  the  Alkaline  Earths,"  are  obtained  from  the  nitrate 
from  which  the  third  group  has  been  removed,  as  explained 
in  Art.  153.  This  nitrate  needs  preliminary  treatment. 
It  is  loaded  down  with  reagents  after  passing  through  the 
operations  required  in  the  preceding  groups.  It  is  best, 
therefore,  to  evaporate  it  strictly  to  dryness,  and  even  to 
ignite  the  residue  gently  in  order  to  expel  these  reagents 
as  far  as  possible.  Then  dissolve  the  residue  in  water, 
when  it  will  be  ready  for  the  fourth  group  reagents. 

Barium,  strontium,  and  calcium  are  precipitated  as  the 
carbonates,  BaCO3,  SrCO3,  and  CaCO3,  by  the  addition  of 
ammonia,  ammonium  chloride,  and  ammonium  carbonate. 
These  metals  are  then  filtered  out,  and  magnesium  is  ob- 
tained directly  from  a  portion  of  the  filtrate  by  adding 
disodium  phosphate,  which  gives  the  double  phosphate, 
MgNH4PO4. 

It  is  evident  that  the  remaining  portion  of  the  filtrate 
148 


BARIUM.  149 

contains,  beside  the  magnesium  that  may  be  present,  the 
fifth  group  metals.  Now  since  magnesium  does  not  inter- 
fere with  the  flame-tests  for  these  metals,  this  portion  of 
the  nitrate  is  retained  for  work  in  the  fifth  group. 


BARIUM. 

177.  Occurrence  and  Preparation.  —  Barium  occurs  only 
in  compounds,  the  chief  of  which  are  heavy  spar,  BaSO4, 
and  Witherite,  BaCO3. 

This  metal  is  not  used  in  the  arts.  It  is  prepared  by 
electrolyzing  a  thick  paste  of  barium  chloride  and  hydro- 
chloric acid  in  the  presence  of  mercury.  The  barium 
amalgam  thus  obtained  is  heated  to  expel  the  mercury, 
thus  yielding  a  porous  mass  of  metallic  barium. 

178.  Properties  and  Compounds.  —  Barium  burns  in  the 
air   with   great   brilliancy.      It   forms   some   useful   com- 
pounds. 

(a)  Barium  Oxide,  BaO,  or  baryta,  is  obtained  by  heat- 
ing the  nitrate  until  nitrous  fumes  cease  to  escape.  From 
this  oxide  barium  hydroxide,  Ba(OH)2,  is  prepared  by  the 
addition  of  water.  Barium  hydroxide  is  largely  used  in 
refining  cane-sugar.  Baryta  water  is  the  solution  of  this 
substance  in  water,  which  is  used  as  a  reagent. 

(#)  Barium  Chloride,  Bad.*,  is  used  in  the  laboratory  as 
a  reagent.  It  is  prepared  by  dissolving  barium  carbonate 
in  hydrochloric  acid. 

(<?)  Barium  Sulphate,  BaSO4,  is  prepared  for  commerce 
by  the  reaction  between  barium  chloride  and  sulphuric 
acid.  It  is  used  as  a  pigment  and  for  weighting  paper. 

(cT)  Barium  Carbonate,  BaCO.{,  is  the  precipitate  ob- 
tained in  analysis.  It  is  soluble  in  acetic  acid. 


150  STRONTIUM. 

179.  Tests  for  Barium.  —  1.  Insoluble  solids  are  fused  on 
charcoal  with   sodium   carbonate   and   then   dissolved  in 
hydrochloric  acid.     The  solution  is  tested  by  2  and  3. 

2.  Solutions  of  barium  salts  are  tested  by  the  addition 
of  reagents  as  follows  :  — 

(a)  Potassium  dichromate  and  ammonia  give  the  yellow 
precipitate,  BaCrO4,  insoluble  in  acetic  acid. 

(6)  Sulphuric  acid  gives  the  white  insoluble  precipitate, 
BaSO4. 

3.  Barium  salts  tinge  the  Bunsen  flame  green  when  they 
are  heated  on  a  loop  of  platinum  wire. 

STRONTIUM. 

180.  Occurrence    and    Preparation.  —  Strontium    occurs 
most   plentifully   in   the    minerals,   celestine,   SrSO4,    and 
strontianite,  SrCO3.     The  metal  is  prepared  in  the  same 
way  as  barium,  excepting  that  the  amalgam  is  heated  in  a 
current  of  hydrogen. 

181.  Properties  and  Compounds.  —  Strontium  is  a  yellow, 
malleable  metal  that  oxidizes  on  exposure  to  the  air,  and 
which  burns  brilliantly  when  heated.     It  is  not  used  in 
the  arts. 

Its  principal  compound  which  is  of  use  is  the  nitrate, 
Sr(NO3)2.  This  salt  is  prepared  by  acting  on  strontium 
carbonate  with  nitric  acid.  Its  principal  use  is  as  an  in- 
gredient of  red  fire  for  tableaux,  etc. 

A  good  mixture  for  red  fire  is  made  by  pulverizing  sep- 
arately equal  parts  of  dried  strontium  nitrate  and  potas- 
sium chlorate.  These  substances  are  then  placed  on  a 
sheet  of  paper  and  an  equal  bulk  of  powdered  gum-shellac 
is  added.  The  whole  is  now  thoroughly  mixed  with  a 


CALCIUM.  151 

spatula.     Friction  or  concussion  must  be  avoided,  as  the 
mixture  is  explosive. 

182.  Tests  for  Strontium.  —  1.  Strontium  maybe  detected 
in  any  compound  by  fusing  it  on  charcoal  with  sodium  car- 
bonate, after  which  the  fused  mass  is  dissolved  in  a  few 
drops  of  hydrochloric  acid.  A  platinum  loop  dipped  in 
the  solution  colors  the  Bunsen  flame  crimson. 

2.  In  its  precipitates  with  most  reagents  strontium  re- 
sembles barium.  But  it  may  be  separated  from  the  latter 


FIG.  31. 

metal  by  potassium  dichromate,  which  gives  the  precipi- 
tate, BaCrO4.  If  this  precipitate  be  filtered  out,  the  stron- 
tium may  be  precipitated  from  the  filtrate  as  the  sulphate, 
SrSO4,  by  the  addition  of  sulphuric  acid.  This  precipitate 
is  then  tested  by  1. 

NOTE.    Care  must  be  used  not  to  mistake  the  pale,  yellowish  red  color 
of  the  calcium  flame  for  that  of  strontium. 


CALCIUM. 

183.  Occurrence  and  Preparation.  —  Calcium  occurs  widely 
distributed  in  compounds,  of  which  the  carbonate,  CaCO3, 
is  the  most  plentiful.  Iceland  spar  is  a  beautiful  variety 
vf  this  carbonate,  possessing  the  property  of  double  refrac- 


152 


CALCIUM. 


tion  (Fig.  31).  Other  crystalline  forms  are  calc  spar,  mar- 
ble, and  dog-tooth  spar.  The  amorphous  varieties  are 
known  as  limestone  and  chalk.  Shells  and  corals  are  also 
mostly  calcium  carbonate.  Calcium  sulphate,  CaSO4,  oc- 
curs in  gypsum,  anhydrite,  and  selenite. 

This  metal  is  not  used  in  the  arts,  and  is  prepared  in  the 
same  way  as  barium  and  strontium. 

184.  Properties  and  Compounds.  —  Calcium  is  a  malleable 
metal  which  is  not  permanent  in  the  air,  and  which  burns 
with  an  orange-yellow  light.  The  compounds  of  calcium 
are  numerous  and  useful.  A  few  of 
these  compounds  are  noted. 

(a)  Calcium  Oxide,  CaO,  or  quick- 
lime, is  prepared  by  roasting  the  car- 
bonate in  lime-kilns  (Fig.  32).  It 
is  used  extensively  for  making 
mortar  and  other  kindred  purposes. 
When  treated  with  water,  calcium 
hydroxide,  Ca(OH)2t  is  obtained. 
This  is  used  as  a  reagent.  Lime 
containing  about  ten  per  cent  of 
silica  is  used  as  a  hydraulic  cement, 
since  it  has  the  property  of  setting 
under  water. 

(5)   G-ypsum,  CaSO4  +  2  H2O,  occurs  native  and  is  much 
used  as  land-plaster.  When  burned,  it  yields  plaster  of  paris. 

(c)  Calcium  Chloride,  CaCl2,  is  obtained  by  treating  lime- 
stone with  hydrochloric  acid.     It  is  used  in  the  laboratory 
as  a  dryer  for  gases. 

(d)  Bleaching-powder  is  obtained  by  passing  chlorine  gas 
into  large  chambers  containing  slaked  lime.     Its  uses  are 
familiar  to  all. 


FIG.  32. 


MAGNESIUM.  153 

(e)  Calcium  Carbonate,  CaCO3,  has  already  been  men- 
tioned. Almost  every  surface  water  contains  this  sub- 
stance in  solution.  It  is  the  principal  substance  which 
makes  waters  "  hard."  Its  action  depends  upon  the  fact 
that  it  replaces  the  sodium  or  potassium  of  the  soap  and 
forms  a  lime  soap  which  is  insoluble.  A  lather  cannot  be 
obtained  in  a  hard  water  until  all  the  hardness  is  thus 
precipitated. 

185.  Tests  for  Calcium.  —  1.  A  solid  is  first  treated  with 
hydrochloric  acid  and  then  tested  by  the  flame-test.      It 
gives  an  orange-red  flame. 

2.  A  solution  of  a  calcium  salt  gives  a  white  precipitate 
with  ammonium  carbonate,  etc.,  the  same  as  barium  and 
strontium.  By  adding  potassium  sulphate  to  a  solution 
containing  all  three  metals  in  solution,  barium  and  stron- 
tium may  be  precipitated  and  filtered  out.  From  the  fil- 
trate calcium  is  then  precipitated  by  ammonium  oxalate, 
(NH4)2C2O4.  A  white  precipitate,  CaC2O4,  is  obtained. 

MAGNESIUM. 

186.  Occurrence     and     Preparation.  —  Magnesium     com- 
pounds   are    widely    distributed.      Magnesium    sulphate, 
MgSO4,  is  a  constituent  of  many  bitter  waters.     In  small 
quantities  it   occurs  in   a   greater  part   of   our  drinking- 
waters.     Magnesite,  MgCO3,  and  dolomite,  CaMg(CO3)2, 
are    quite   common    compounds.     Asbestos,   (MgCa)SiO3, 
talc,  Mg3H2(SiO3)4,  and  meerschaum,  Mg2H2(SiO3)3,  are 
well  known." 

Magnesium  is  prepared  for  commerce  by  fusing  a  mix- 
ture of  the  dry  chloride,  fluorspar  and  metallic  sodium  in 
a  closed  crucible.  The  metal  thus  obtained  is  purified  by 


154  MAGNESIUM. 

distillation.  When  in  a  semi-molten  condition  it  is  drawn 
into  wire,  which  usually  is  finally  flattened  to  form  the 
magnesium  ribbon  of  commerce. 

187.  Properties  and  Compounds.  —  Magnesium  is  a  silver- 
white  metal  which  is  quite  permanent  in  dry  air.    It  burns 
readily,  emitting  a  painfully  bright  and  dazzling  light  that 
is  rich  in  chemical  rays.     It  is  used  in  photography  for 
illuminating  dark  places,  such  a  caverns,  in  order   that 
they  may  be  photographed.     It  is  also  employed  in  pyro- 
technics and  for  signaling. 

(#)  Magnesia,  MgO,  is  obtained  by  igniting  the  carbon- 
ate. It  is  used  in  medicine. 

(6)  Magnesium  Chloride,  MgCl2,  is  obtained  from  sea- 
water  and  from  salt  wells.  It  is  used  in  dressing  cotton 
goods. 

(c)  Magnesium  Sulphate,  MgSO4,  is  known  as  Epsom 
salts.     It  is  obtained  from  the  waters  of  some  springs.     It 
is  also  prepared  by  treating  the  carbonate  with  sulphuric 
acid.     It  is  much  used  as  a  cathartic  and  in  dressing  cot- 
ton goods. 

(d)  Magnesium  Carbonate,  MgCO3,  is  obtained  from  dol- 
omite.    It  is  used  in  medicine ;  it  also  is  used  as  a  face- 
powder. 

188.  Test  for   Magnesium.  —  After  removing   the  other 
fourth  group  metals  with  ammonia,  ammonium  chloride, 
and  ammonium  carbonate,  magnesium  may  be  obtained  as  a 
white  crystalline  precipitate,  MgNH4PO4,  by  adding  to  the 
filtrate  disodium  phosphate.     Under  these  circumstances 
no  further  test  is  necessary. 


SEPARATION    OF    THE   FOURTH    GROUP   METALS.       155 


SEPARATION    OF    THE    FOURTH    GROUP    METALS. 

189.  Barium,  strontium,  and  calcium  are  precipitated  as 
the  carbonates,  BaCO3,  SrCOg,  and  CaCO3,  as  explained  in 
Art.  176.  The  precipitate  is  then  filtered  out,  and  mag- 
nesium is  precipitated,  as  explained  in  the  same  article. 
If  a.  precipitate  is  obtained  in  that  place,  no  further  identi- 
fication of  magnesium  is  necessary. 

The  precipitate  containing  the  first  three  metals  is  first 
dissolved  in  acetic  acid.  The  solution  obtained  is  then 
treated  as  follows  :  — 

(a)  To  the  solution  add  ammonia  till  alkaline  ;  then 
add  potassium  dichromate.  If  barium  be  present,  it  will  be 
precipitated  as  barium  chromate,  BaCrO4.  Filter.  Dis- 
solve the  precipitate  in  hydrochloric  acid  and  then  add 
sulphuric  acid;  a  white  precipitate,  BaSO4,  insoluble  in 
acids,  confirms  the  presence  of  barium. 

(£>)  To  the  filtrate  from  (a)  add  potassium  sulphate.  A 
white  precipitate,  SrSO4,  indicates  the  presence  of  stron- 
tium. Filter.  Test  the  precipitate  by  Art.  182, 1,  to  make 
sure  strontium  is  present. 

(<?)  To  the  filtrate  from  (b)  add  ammonium  oxalate, 
(NH4)2C2O4.  A  white  precipitate  in  this  place  insures  the 
presence  of  calcium. 

NOTE.  If  no  barium  be  present,  it  is  best  not  to  add  the  potassium 
dichromate.  By  testing  a  small  portion  of  the  acetic  acid  solution  for 
barium,  the  presence  or  absence  of  that  metal  may  be  determined. 


CHAPTER   XIV. 

THE   FIFTH   GROUP    METALS. 

DATA  FOR  COMPUTATIONS.  —  POTASSIUM  :  Symbol,  K' ;  Atomic  Weight, 
39;  Specific  Heat,  0.1655  ;  Melting-point,  62.5° ;  Specific  Gravity,  0.87. 
—  SODIUM  :  Symbol,  Na' ;  Atomic  Weight,  23 ;  Specific  Heat,  0.2394 ; 
Melting-point,  95.6° ;  Specific  Gravity,  0.978. 

190.  The  fifth  group  metals  are  often  called  the  "  Metals 
of  the  Alkalies."     They  do  not  furnish  precipitates  with 
ordinary  reagents ;  but  they  are  detected  by  the  color  of 
the  flame  obtained  when  any  of  their  salts  are  placed  in 
the  Bunsen  flame  on  a  platinum  loop. 

In  case  other  metals  are  in  the  solution,  they  must  all  be 
removed  except  magnesium,  as  explained  in  Art.  176. 

POTASSIUM. 

191.  Occurrence  and  Preparation.  —  The  potassium  com- 
pounds are  widely  distributed.     They  occur  in  sea-water, 
in  many  mineral  waters,  and  in  all  fruitful  soils.     They 
form  essential  constituents  of  plants.     Sylvite,  KC1 ;  salt- 
petre, KNO3 ;  and  potassium  sulphate,  K2SO4,  are  some  of 
the  most  commonly  occurring  compounds.     But  potassium 
is  also  a  constituent  of  many  of  the  older  rocks,  in  which 
it  occurs  in  orthoclase. 

In  preparing  potassium  for  commerce,  acid  potassium 
tartrate  is  first  heated  in  closed  iron  retorts.     This  gives 
an  intimate  mixture  of  potassium  carbonate  and  carbon. 
166 


POTASSIUM. 


157 


This  mixture  is  now  placed  in  iron  tubes  covered  with  fire- 
clay, and  then  placed  in  a  furnace  and  heated  to  a  white 
heat  (Fig.  33).  Metallic  potassium  is  obtained  in  the 
form  of  a  vapor,  which  is  condensed  in  a  shallow  box  con- 
denser placed  outside  the  furnace.  While  in  a  liquid 
state  it  flows  into  vessels  containing  rock  oil. 


FIG.  33. 

A  is  the  iron  tube  retort  coated  with  clay. 

C  is  the  condenser. 

D  is  the  cup  containing  rock  oil. 

192.  Properties  and  Compounds  of  Potassium.  —  Potassium 
is  a  silver-white  metal  when  first  cut,  but  it  soon  shows  a 
bluish  surface  on  exposure.  It  ignites  at  a  low  tempera- 
ture, and  must  be  handled  with  pincers.  It  decomposes 
water  at  ordinary  temperatures,  often  with  explosive  vio- 
lence, hydrogen  being  liberated  and  potassium  hydroxide 
being  formed. 

The  potassium  salts  are  highly  valued,  owing  to  their 
solubility  in  water  and  their  adaptability  for  various  medi- 


158  POTASSIUM. 

cinal  and  industrial  uses.  The  potassium  salt  of  nearly 
every  acid  is  an  article  of  commerce.  Space  allows  but 
few  compounds  to  be  mentioned. 

(a)  Potassium  Hydroxide,  or  caustic  potash,  KOH,  is 
prepared  by  treating  potassium  carbonate  with  slaked  lime. 
The  crude  article  is  much  used  as  a  lye.  The  form  em- 
ployed for  laboratory  work  is  purified  before  it  is  cast  into 
sticks. 

(6)  Potassium  Iodide,  KI,  is  obtained  from  a  warm,  con- 
centrated solution  of  potassium  hydroxide  by  adding  iodine 
until  the  potassium  is  satisfied.  The  salt  obtained  is  ignited 
to  decompose  any  iodate  that  may  be  formed.  The  bro- 
mide, KBr,  is  obtained  in  a  similar  way  by  the  use  of  liquid 
bromine. 

(c)  Potassium  Chlorate,  KC1O3,  is  obtained  by  passing 
chlorine  gas  through  a  solution  of  calcium  hydroxide  until 
calcium  chlorate  is  formed.  That  salt  is  then  decomposed 
by  treatment  with  potassium  chloride  :  — 

Ca(C103)2  +  2  KC1  =  CaCljj  +  2  KC103. 

(t?)  Potassium  Nitrate,  or  saltpetre,  KNO3,  occurs  as  an 
incrustation  on  the  soil  in  some  hot,  dry  countries,  as  in 
India  and  Egypt.  It  is  produced  through  the  agency  of 
minute  organisms  or  ferments  which  cause  the  nitrogen  of 
organic  substances  to  combine  with  the  potassium  com- 
pounds of  the  soil.  In  the  "  saltpetre  plantations  "  heaps 
of  refuse  animal  matter  are  mixed  with  wood  ashes  and 
lime,  and  then  moistened  with  urine  or  stable  drainings. 
At  intervals  the  outer  layer  is  removed  and  leached  with 
water  to  extract  the  nitrate. 

This  useful  compound  is  also  obtained  by  treating  Chili 
saltpetre  with  potassium  chloride  :  - 

NaNOa  +  KC1  =  KK03  +  NaCl. 


SODIUM.  159 

Potassium  nitrate  is  extensively  used  in  the  manufacture 
of  gunpowder,  which  is  an  intimate  mixture  of  potassium 
nitrate,  sulphur,  and  pulverized  charcoal.  In  the  labora- 
tory this  salt  is  used  in  many  ways,  as  demonstrated  by 
work  previously  done. 

(e)  Potassium  Carbonate,  or  potash,  K2CO3,  is  obtained 
by  leaching  wood  ashes.  The  solution  is  evaporated  to 
saturation,  when  this  salt  crystallizes  out  in  impure  forms, 
which  are  afterward  purified  by  roasting  in  a  reverbera- 
tory  furnace. 

193.  Tests  for  Potassium.  —  Potassium  compounds  on  a 
platinum  loop  color  the  Bunsen  flame  violet.     This  flame 
is  visible  through  thick  blue  glass. 

SODIUM. 

194.  Occurrence  and  Preparation.  —  Sodium  is  distributed 
everywhere.     The  most  plentiful  compound  is  the   chlo- 
ride, or  common  salt.     Salt  is  obtained  from  sea-water  and 
from  salt  wells  in  various  parts  of  the  world.     Vast  depos- 
its of  rock  salt  are  found  in  different  places.     The  brine 
from   salt  wells  is   pumped   into   large   evaporating-pans 
heated   by  steam  coils.     When    the   brine  is  sufficiently 
concentrated,  crystals  of  salt  separate  out,  and  these  are 
removed  from  the  mother  liquors  by  means  of  perforated 
scoops. 

Rock  salt  is  usually  mined ;  but  at  Marine  City,  Mich., 
the  deposits  are  too  deep  for  that  method.  Therefore  wells 
are  bored  doAvn  to  the  salt  rock,  and  streams  of  water  are 
forced  in.  When  this  water  has  become  saturated,  it  is 
raised  into  pans  and  evaporated  the  same  as  any  brine. 

In  the  United  States  salt  is  manufactured.^!  Syracuse, 


160  SODIUM. 

N.Y.,  and  in  the  Saginaw  Valley,  Mich.     Other  localities 
also  afford  salt  in  smaller  quantities. 

Sodium  is  prepared  in  the  same  way  as  potassium,  ex- 
cept that  the  carbonate  and  charcoal  are  employed  in  the 
reduction. 

195.  Properties  and  Compounds.  —  Sodium  is  a  metal 
closely  resembling  potassium  in  its  physical  and  chemical 
properties,  but  it  is  not  so  energetic  in  its  action  upon 
water.  It  will  take  fire  in  warm  water,  in  starch  paste, 
or  on  wet  paper. 

The  compounds  of  sodium  are  as  numerous  and  as  use- 
ful as  those  of  potassium.  The  salts  are  prepared  by  about 
the  same  methods,  and  their  uses  are  similar  to  the  potas- 
sium salts.  But  the  sodium  salts  are  not  so  well  adapted 
for  some  uses.  Thus,  sodium  nitrate  does  not  make  good 
gunpowder,  owing  to  its  greater  liability  to  effloresce  and 
to  attract  moisture.  Again,  many  chemists  prefer  the 
potassium  salts  as  reagents,  since  they  do  not  "  creep  "  out 
between  the  stopper  and  the  neck  of  the  bottle  so  much  as 
the  sodium  compounds. 

Many  sodium  compounds  have  already  been  noticed,  and 
the  limits  of  this  work  will  warrant  a  notice  of  but  few 
others. 

(a)  Sodium  Carbonate,  Na2CO3,  is  extensively  used  for 
various  purposes.  It  is  obtained  from  common  salt  by  first 
converting  the  chloride  into  sodium  sulphate  by  means  of 
sulphuric  acid.  The  sulphate  is  next  heated  with  pow- 
dered coal,  when  it  is  reduced  to  sodium  sulphide  ;  then 
this  sulphide  is  heated  with  limestone,  when  it  is  converted 
into  the  carbonate.  Usually  the  coal  and  limestone  are 
added  at  the  same  time.  The  sodium  carbonate  thus 
obtained  is  now  removed  by  lixiviation  with  water,  after 


AMMONIUM.  161 

which  the  solution  is  evaporated  to  dryness  and  then  cal- 
cined, when  it  is  ready  for  the  market. 

The  ammonia  process  for  making  sodium  carbonate  is 
now  extensively  used.  In  this  process  sodium  chloride  is 
simply  treated  with  ammonia  and  carbon  dioxide.  Acid 
sodium  carbonate,  NaHCO3,  is  first  formed.  Then  this 
compound  is  decomposed  by  heat  into  the  normal  carbon- 
ate and  carbon  dioxide. 

Soda  crystals  or  sal  sodae,  Na2CO3  +  10  H2O,  is  obtained 
by  allowing  the  common  carbonate  to  crystallize  out  of  a 
water  solution.  It  is  used  in  softening  water. 

Acid  sodium  carbonate,  NaHCOg,  is  used  for  domestic 
purposes  as  saleratus  and  as  an  ingredient  of  baking-pow- 
ders. It  is  often  called  bicarbonate  of  soda. 

(5)  Glass  is  a  silicate  of  calcium  and  sodium  or  of  cal- 
cium and  potassium.  Ordinary  glass  contains  sodium. 
The  difficultly  fusible  Bohemian  glass  contains  potassium. 
Glass  used  for  optical  purposes  and  for  making  some  kinds 
of  fine  glassware  contains  lead.  Green  bottle  glass  owes 
its  color  to  the  presence  of  iron. 

Ordinary  glass  is  made  by  fusing  a  mixture  of  quartz, 
quicklime,  and  sodium  carbonate.  Sometimes  limestone  is 
used  in  place  of  the  quicklime. 

196.  Test  for  Sodium.  —  Any  sodium  compound  on  the 
platinum  loop  colors  the  Bunsen  flame  yellow.    This  flame 
is  not  visible  through  the  blue  glass. 

AMMONIUM. 

197.  Ammonium  is  a  hypothetical  compound,  NH4,  which 
resembles  a  metal  in  some  respects.     We  have  already 
seen  how  this  combines  with  acids  to  form  salts.     Thus, 


162      IDENTIFICATION   OF  THE   FIFTH   GROUP   METALS. 

we  have  had  ammonium  chloride,  NH4C1,  ammonium 
nitrate,  NH4NO3,  and  other  salts.  Again,  it  seems  that 
ammonium  is  capable  of  forming  an  amalgam  with  mer- 
cury, which  may  be  prepared  by  adding  sodium  amalgam 
containing  from  one  to  three  per  cent  of  sodium,  to  a 
strong  solution  of  ammonium  chloride.  But  notwithstand- 
ing these  considerations,  ammonium  has  not  been  isolated. 

The  ammonium  salts  may  usually  be  made  by  adding 
the  acid  directly  to  ammonia,  NH3.  In  the  case  of  ammo- 
nium carbonate,  (NH4)2CO3,  ammonium  chloride  is  sub- 
limed with  calcium  carbonate,  after  which  the  product  is 
digested  with  strong  aqua  ammoiiise. 

Ammonium  sulphide,  (NH4)2S,  is  obtained  in  the  labo- 
ratory for  reagent  purposes  by  passing  hydrogen  sulphide 
through  reagent  ammonia  until  it  will  not  give  a  precipi- 
tate with  a  solution  of  magnesium  sulphate.  Upon  stand- 
ing, this  sulphide  changes  to  the  yellow  ammonium  sul- 
phide, (NH4)2Sx,  spoken  of  in  the  second  group  metals. 
This  yellow  sulphide  may  also  be  obtained  by  warming 
ordinary  ammonium  sulphide  with  flowers  of  sulphur ;  the 
operation  may  be  conducted  in  a  test-tube,  and  the  reagent 
may  be  prepared  in  small  quantities  from  time  to  time  as 
needed. 

IDENTIFICATION    OP    THE    FIFTH    GROUP    METALS. 

198.  Both  sodium  and  potassium  are  detected  by  the 
flame-test.  If  both  are  present,  the  yellow  sodium  flame  is 
liable  to  obscure  the  potassium  flame.  But  when  viewed 
through  the  blue  glass,  the  sodium  flame  is  shut  off  while 
the  potassium  flame  remains  visible. 

Ammonium  is  always  to  be  sought  in  the  original  solu- 
tion. In  the  course  of  analysis  so  much  ammonia  is  em- 


ANALYSIS   OF   AN   UNKNOWN   SUBSTANCE.  163 

ployed  that  the  solution  tested  for  sodium  and  potassium 
would  always  give  the  test  for  ammonium. 

Therefore  add  potassium  hydroxide  to  the  original  solu- 
tion, warm  gently,  and  test  the  escaping  fumes  for  ammo- 
nia by  the  odor,  and  with  a  glass  rod  moistened  with 
hydrochloric  acid,  etc.,  as  in  Art.  33. 


ANALYSIS   OF   AN   UNKNOWN   SUBSTANCE. 
I. 

TO   DISSOLVE   A   SOLID. 

199.  If  the  unknown  be  in  solution,  proceed  immediately 
by  II.  If  the  substance  be  a  solid  (excepting  such  a  sub- 
stance as  sulphur  or  iodine),  it  is  best  to  bring  it  into  solu- 
tion. This  is  not  always  easy  to  do,  and  some  methodical 
plan  ought  to  be  followed,  such  as  the  one  here  given :  — 

1.  Place  the  substance  in  an  evaporating-dish,  add  water, 
and  boil.     If  the  substance  dissolve  completely,  treat  the 
solution  by  II.     If  it  be  doubtful  whether  any  of  the  sub- 
stance has  dissolved,  evaporate  carefully  to  dryness  (on  a 
piece  of  porcelain  or  on  platinum  foil)  a  few  drops  of  the 
liquid  in  the  dish.     If  a  residue  remain,  some  of  the  sub- 
stance has  dissolved.    Filter  out  the  solid  remaining  in  the 
evaporating-dish,  and  treat  the  nitrate  as  in  II. ;  proceed  by 
2  with  the  remaining  solid. 

If  none  of  the  solid  has  dissolved,  proceed  with  it  by  2. 

2.  Add  nitric  acid  to  the  contents  of  the  evaporating- 
dish,  and  boil  gently.    If  the  substance  dissolve  completely, 
evaporate    the  solution  nearly  to   dryness   to  expel   any 
excess  of  acid  ;  dissolve  the  residue  in  water,  and  treat  the 
solution  by  II. 

If  it  be  doubtful  whether  any  of  the  substance  has  dis- 


164  ANALYSIS   OF   AN   UNKNOWN   SUBSTANCE. 

solved,  test  a  few  drops  on  porcelain  as  before.  If  a  part 
has  dissolved,  filter,  evaporate  the  filtrate  to  expel  any 
excess  of  acid,  add  water,  and  then  proceed  by  II.  Treat 
the  residue  by  3. 

If 'none  of  the  substance  has  dissolved,  treat  the  solid 
by  3. 

3.  Add  nitro-hydrochloric  acid  to  the   contents   of   the 
evaporating-dish,  and  warm  gently.     If  the  substance  dis- 
solve completely,  expel  the  excess  of  acid,  etc.,  as  in  2. 

If  it  be  doubtful  whether  any  of  the  substance  has  dis- 
solved, test  on  porcelain,  etc.,  as  before. 

If  a  portion  of  the  solid  dissolve,  filter,  expel  any  excess 
of  acid,  etc.,  as  before.  Treat  the  residue  by  4. 

If  none  of  the  substance  has  dissolved,  it  is  insoluble  in 
acids,  and  must  be  treated  as  in  4. 

4.  Fuse  the  insoluble  substance  on  charcoal  with  sodium 
carbonate,  and  then  commence  back  again  by  1.     The  mass 
will  usually  dissolve  either  in  water  or  in  nitric  acid. 

In  fusing,  note  any  coating  around  the  assay. 

II. 

SEPARATION    AND   DETECTION    OF   BASES. 

1.  Add  hydrochloric  acid  to  the  solution ;  a  white  pre- 
cipitate indicates  any  or  all  of  the  first  group  metals  in  the 
form  of  the  chlorides  :  PbCl2 ;  AgCl ;  Hg2Cl2.     Filter  out 
the  precipitate,  and  proceed  with  it  as  by  Art.  131.     Treat 
the  filtrate  by  2. 

2.  Through  the  filtrate  from  2  pass  hydrogen  sulphide 
for  a  long  time.     A  precipitate  may  contain  any  or  all  of 
the  second  group  metals  in  the  form  of  the  sulphides : 
As2S3  (yellow) ;    Sb2S3  or  Sb2S5  (orange) ;  SnS  (brown) ; 


ANALYSIS   OF   AN    UNKNOWN   SUBSTANCE.  165 


SnS2  (yellow);   Bi^  (black);    CuS  (black);    CdS  (yel- 
low); PbS  (black);  HgS  (black). 

Filter,  and  treat  the  precipitate  by  Art.  150.  Boil  the 
filtrate  to  expel  all  hydrogen  sulphide,  add  a  few  drops  of 
nitric  acid,  boil  again  for  a  short  time,  and  proceed  by  3. 

3.  To  the  prepared  nitrate  from   2  add  ammonia  and 
ammonium  chloride;  any  precipitate   may  be:   Fe2(OH)6 
(reddish   brown);    Cr2(OH)6   (bluish   green);    A12(OH)6 
(white,  gelatinous).    Filter.    Treat  the  precipitate  by  Art. 
175,1. 

To  the  nitrate  add  ammonium  sulphide.  Any  precipi- 
tate may  be  :  MnS  (flesh-colored)  ;  CoS  (black)  ;  NiS 
(black);  ZnS  (white).  Filter,  and  treat  the  precipitate 
by  Art.  175,  II. 

Evaporate  the  filtrate  to  dryness,  gently  ignite  the  resi- 
due to  expel  as  much  of  the  reagents  previously  added  as 
possible,  dissolve  the  residue  in  water,  and  proceed  by  4. 

4.  To  the  prepared  filtrate  from  3  add  ammonia,  ammo- 
nium  chloride,  and   ammonium    carbonate.     A  precipitate 
may  be  the  carbonates  (white):  BaCO3;  SrCO3;  CaCO3. 
Filter,  and  test  the  precipitate  by  Art.  189.     Divide  the  fil- 
trate in  two  parts  ;   to  one  of  these  parts  add  disodium 
phosphate  ;    a    white    precipitate,    NH4MgPO4,    identifies 
magnesium. 

5.  Test  the  second  part  of  the  filtrate  from  4  by  Art. 
198.     Test  the  original  solutions  for  ammonium  by  Art. 
33. 

III. 

DETECTION   OF   ACIDS. 

1.  If  the  unknown  is  a  solution  or  a  solid  soluble  in 
water  and  has  been  found  by  the  work  in  II.  to  contain 


166  ANALYSIS    OF    AN    UNKNOWN    SUBSTANCE. 

arsenic,  chromium,  or  manganese,  these  elements  may  be 
present  in  the  unknown  as  acids.  Therefore  test  the  sub- 
stance for  the  acids  formed  by  these  elements. 

2.  If  these  metals  are  not  present,  but  other  metals 
belonging  to  any  group  (except  the  fifth  group  metals  and 
magnesium)  have  been  found,  it  is  necessary  to  remove 
these  bases  before  testing  for  acids.  This  is  accomplished 
by  adding  to  the  solution,  potassium  hydroxide  and  potas- 
sium carbonate.  These  reagents  remove  all  metals  that 
would  interfere  with  the  tests  for  acids.  Filter  out  the 
precipitate,  and  treat  the  filtrate  by  (a),  etc.  If  no  bases 
are  present  in  the  solution  that  interfere  with  the  acid 
tests,  proceed  by  (a),  etc. 

(a)  Acidulate  a  portion  of  the  solution  or  filtrate  with 
nitric  acid  and  add  barium  chloride,  BaCl2.  A  white  pre- 
cipitate, BaSO4,  shows  that  sulphuric  acid  is  present. 

(6)  Acidulate  a  second  portion  of  the  solution  or  filtrate 
with  nitric  acid  and  add  silver  nitrate.  A  white  precipi- 
tate indicates  the  presence  of  any  of  these  acids :  HC1 ; 
HBr;  HI,  HCN.1  Therefore  to  a  fresh  portion  of  the 
solution  or  filtrate  add  hydrochloric  acid,  chlorine  water, 
and  carbon  disulphide,  and  shake.  No  color  indicates  HC1 
or  HCN.  Try  the  odor  of  the  unknown ;  an  odor  of 
peach  blossoms  indicates  HCN  ;  test  further  by  Art.  93. 
If  no  odor  is  noticeable,  the  work  up  to  this  point  shows 
hydrochloric  acid,  HC1,  to  be  present. 

If  the  carbon  bisulphide  is  colored  brownish  red,  HBr  is 
present.  If  the  color  is  violet,  HI  is  present. 

(c)  Acidulate  a  third  portion  of  the  solution  or  filtrate 


1  H4Fe(CN)6  and  H3Fe(CN)6  would  give  precipitates  here.  But  the 
student  would  probably  discover  these  acids  while  working  for  the  bases. 
If  indications  of  these  acids  are  observed,  test  by  Art.  156,  2  and  3. 


ANALYSIS    OF   AN   UNKNOWN    SUBSTANCE.  167 

with  hydrochloric  acid,  and  test  for  nitric  acid,  Art.  42. 
(See  note.) 

(oT)  If  carbonic  acid  be  present,  it  may  be  found  by  add- 
ing to  the  original  substance  hydrochloric  acid.  A  brisk 
effervescence  will  ensue. 

(e)  Now  test  separate  portions  of  the  solution,  or  nitrate 
for  the  following  acids :  H3PO4;  H4SiO4;  H3BO3;  H2S2O3; 
HC103. 

3.  If  the  substance  be  an  oxide  or  a  hydroxide,  it  will 
give  no  tests  for  acids. 

4.  If  the  substance  be  in  the  form  of  a  powder  or  a  solid, 
one  may  tell  nearly  what   acids  are  present   by  placing 
some  of   the  dry  powder  in  a  test-tube  and  adding  sul- 
phuric acid.     Upon  heating  gently  the  following  phenom- 
ena may  occur :  — 

(a)  A  rapid  effervescence  of  an  odorless,  colorless  gas 
indicates  a  carbonate. 

(5)  A  slower  effervescence  of  a  colorless  gas  possessing 
the  odor  of  rotten  eggs  indicates  a  sulphide.  An  odor  of 
burning  matches  indicates  a  sulphite  or  a  thio-sulphate. 
An  odor  of  peach  blossoms  indicates  a  cyanide.  An  odor 
of  vinegar  indicates  an  acetate.  An  irritating  odor  indi- 
cates a  chloride,  a  fluoride,  or  a  nitrate. 

(tf)  A  colored  gas  with  an  irritating  odor  indicates  an 
iodide  or  a  bromide. 

(d)  A  sudden  explosion  identifies  a  chlorate. 

(<?)  If  no  action  occurs,  the  acid  may  be  H2SO4 ;  H3PO4 ; 
H4SiO4;  H3BO3.  Therefore  test  for  these  acids  in  order. 

NOTE.  It  must  be  distinctly  understood  that  the  scheme  outlined  in  4 
only  gives  indications.  These  indications  are  not  sufficiently  positive  to 
permit  an  acid  (except  chloric  acid)  to  be  reported  without  further  tests. 
Therefore  when  an  indication  is  obtained,  turn  to  the  acid  indicated  and 
make  the  tests  there  given. 


CHAPTER   XV. 

INTRODUCTORY  TO   THE   CARBON   COMPOUNDS. 

200,  Organic  and  Inorganic  Substances.  —  In  former  times 
all  compounds  were  classified  into  organic  and  inorganic 
substances.  This  classification  was  based  upon  the  sup- 
position that  the  so-called  organic  substances  could  be  pro- 
duced only  through  the  intervention  of  living  organisms, 
i.e.  plants  and  animals.  Starch,  sugar,  indigo,  and  urea 
will  serve  as  examples  of  the  so-called  organic  substances, 
while  any  of  the  salts  or  ores  previously  considered  will 
afford  examples  of  the  inorganic  compounds. 

In  these  later  days,  however,  so  many  of  the  so-called 
organic  compounds  have  been  prepared  in  the  laboratory, 
by  artificial  processes,  that  it  has  become  evident  that  the 
name  "  organic  "  is  not  at  all  appropriate,  nor  was  the 
former  distinction  well  taken.  In  short,  even  "  Organic 
Chemistry,"  according  to  our  better  understanding,  is  now 
usually  termed  the  Chemistry  of  the  Carbon  Compounds, 
or,  better  still,  the  Chemistry  of  the  Hydrocarbons  and 
their  Derivatives. 

The  carbon  compounds  are  almost  innumerable  in  num- 
ber ;  and  they  vary  in  their  structure  from  simple  forms  to 
those  of  the  greatest  complexity.  Carbon,  as  we  have  seen, 
is  quadrivalent ;  and,  moreover,  it  seems  to  possess  the 
property  of  combining  with  itself  to  form  centres,  around 
which  the  remaining  elements  of  the  more  complex  com- 
pounds are  held  by  the  usual  laws  of  valence.  Thus  it 

168 


INTRODUCTORY   TO   THE   CARBON   COMPOUNDS.       169 

appears  that  an  infinite  number  of  carbon  compounds  are 
possible,  and  that  their  complexity  may  be  very  great. 

201.  Homology.  —  At  the  outset  it  would  seem  desirable 
to  arrange  the  carbon  compounds,  if  possible,  into  classes, 
so  that  some  order  might  be  introduced  into  their  consid- 
eration. Fortunately,  this  may  be  done.  Thus,  if  we 
examine  the  formulae  of  the  compounds  CH4,  C2H6,  C3H8, 
C4H10,  C5H12,  etc.,  we  shall  see  that  there  are  evident  rela- 
tions existing.  In  the  first  place,  it  appears  that  between 
any  consecutive  two  of  these  compounds  there  is  a  con- 
stant difference  in  composition  of  CH2 ;  and  in  the  second 
place,  it  is  evident  that  these  compounds  form  a  natural 
series,  all  members  of  which  may  be  represented  by  one 
general  formula.  Thus,  CnH2n+2  will  represent  any  mem- 
ber in  the  foregoing  series.  'This  series  is  a  well-known 
one,  and  is  called  the  marsh  gas,  or  paraffin,  series.  Such 
a  relation  between  compounds  is  termed  Homology,  and 
such  a  series  is  called  a  Homologous  Series. 

In  all  there  are  at  present  known,  to  a  greater  or  less 
extent,  about  eighteen  of  these  homologous  series ;  and  it 
matters  not  what  one  of  the  numerous  compounds  of  car- 
bon may  be  under  consideration,  nor  how  complex  its  struc- 
ture may  be,  it  can  usually  be  assigned  to  some  one  of  these 
series.  Some  compounds,  however,  belong  to  more  than 
one  series. 

In  the  following  article  a  table  is  given  for  inspection 
which  gives  the  names  of  these  different  series,  together 
with  some  other  facts  that  will  be  useful. 

If  we  begin  with  the  lowest  member  of  any  of  these 
homologous  series  and  add  successively  CH2,  it  is  evident 
that  the  series  is  capable  of  extension  to  infinity.  But  as 
a  matter  of  fact,  the  number  of  hydrocarbons  in  any  series, 


170       INTRODUCTORY   TO   THE   CARBON   COMPOUNDS. 


so  far  as  known,  is  quite  limited.  In  the  first,  or  paraffin, 
series,  CH4,  C2H6,  etc.,  the  series  is  known  to  extend  to 
CggHre,  and  sixteen  terms  have  been  described.  In  several 
other  series  but  one  member  is  known,  while  still  others 
have  but  from  two  to  four  representatives.  In  the  six- 
teenth series  not  a  single  term  is  known.  But  these 
series  are  important,  since  their  different  members  are 
now  considered  to  be  the  starting-points  from  which  all 
the  various  compounds  are  derived.  It  will  be  noticed 
that  these  substances  contain  carbon  and  hydrogen  only, 
and  in  general  they  are  termed  Hydrocarbons. 

202.   A  Table  of  the  Hydrocarbon  Series. 


Name  of  Series. 

General 
Formula. 

Lowest  Member  known. 

Formula 
Lowest 
Member. 

Paraffin 

r  w 

Methane 

CH4 

Olefine  

CnH2w 

Ethylene 

C0H,t 

Acetylene 

Acetylene 

CoH9 

Terpene     
Benzene     ... 

CnH2n_4 

Valylene 
Benzene 

C5H6 
C«H« 

Cinnamene,  or  Styrene  .     . 
Acetenyl-Benzene  .... 
Naphthalene  .              ... 

CnH2n_8 
CMH2»-10 

Styrene 
Phenyl-  Acetylene 
Naphthalene 

C8Hg 
C8H6 

Diphenyl 

Diphenyl 

Stilbene     . 

Acetylene-Naphthalene 

Ci2H8 

Anthracene   
Benzyl-Naphthalene  .    .     . 
Pyrene  . 

CnHgn-18 

CnH2»_20 

Anthracene 
Benzyl-Naphthalene 
Pyrene 

QuHio 

Ci7H]4 

Chrysene  

CnH2n    24 

Chrysene 

CigHi2 

Dinaphthyl 

Dinaphthyl 

C^Hu 

Tdrialene   

CwH2n-28 

Tdrialene 

C22Hi4 

Tetraphenyl-Ethylene     .     . 

CnH2n_32 

Tetraphenyl-Ethylene 

C-fcHa, 

INTRODUCTORY   TO   THE   CARBON   COMPOUNDS.       171 

203.  Names  of  the  Members  of  the  Hydrocarbon  Series.— 
In  the  first  or  paraffin,  series,  tne  ending  "  ane  "  is  used 
as  a  distinctive  ending,  while  in  all  other  series  the  names 
of  the  members  usually  end  in  uene."  In  the  first  two 
series,  after  the  first  four  members,  the  numeral  prefixes, 
;'pent,"  "  hex,"  "  sept,"  etc.,  are  used  to  distinguish  the  dif- 
ferent compounds.  The  subjoined  lists  will  illustrate  the 
principles  used  in  naming  the  first  two  series :  — 


PARAFFIN  SERIES. 


CH4  .     .     .  Methane. 

C2H6  .     .     .  Ethane. 

C3H8  .     .     .  Propane. 

C4H10  ...  Butane. 

C5H12  .     .     .  Pentane. 

C6H14  .     .     .  Hexane. 
Etc.,  etc. 


OLEFINE  SERIES. 


CnH 


2n. 


C2H4  .  .  .  Ethylene. 

C3H6  .  .  .  Propylene. 

C4H8  .  .  .  Butylene. 

C5H10  .  .  .  Amylene. 

C6H12  .  .  .  Hexylene. 

C7H14  .  .  .  Heptylene. 

Etc.,  etc. 


In  naming  the  members  of  the  remaining  series,  no  such 
regular  method  has  been  followed.  The  names  are  mostly 
compounded  from  simpler  ones  which  correspond  to  simple 
radicals,  of  which  the  higher  series  may  be  said  to  be  com- 
posed. When  the  names  are  not  compound,  they  frequently 
indicate  the  source  from  which  the  member  is  obtained,  or 
some  striking  peculiarity  belonging  to  that  member.  But 
it  is  not  necessary  for  the  beginner  to  master  all  these 
names.  Some  of  the  most  important  will  be  noticed  in 
appropriate  places. 

204.  Elementals  and  Derivatives.  —  In  the  previous  chap- 
ters of  this  work  we  were  dealing  with  elements  and  with 
the  compounds  formed  by  the  union  of  these  elements.  A 
somewhat  similar  distinction  may  be  made  in  the  study  of 


172       INTRODUCTORY  TO  THE  CARBON  COMPOUNDS. 

the  carbon  compounds.  It  is  now  customary  to  consider 
those  hydrocarbons  which  form  the  members  of  the  different 
homologous  series  as  primary  compounds.  The  more  com- 
plex compounds,  which  contain  other  elements  besides  car- 
bon and  hydrogen,  are  regarded  as  derivatives  of  the  simpler 
hydrocarbons.  The  principal  derivatives  are  of  four  kinds :  — 

1.  Those  containing  chlorine,  bromine,  and  iodine.  These 
are  termed  in  general  the  Halogen  Derivatives. 

2.  Those  containing  oxygen.      Under  this  division  are 
included  such  important  compounds  as  the  Alcohols,  Uthers, 
and  Acids. 

3.  Those  containing  nitrogen.     These  are  formed  by  the 
reaction  between  certain  hydrocarbons  and  such  reagents 
as  nitric  acid  and  ammonia  and  cyanogen.    Those  obtained 
from  ammonia  are  termed  Amines;  e.g.  NH2CH3,  methyl- 
amine.     Those  from  nitric  acid  and  cyanogen  are  called 
respectively  Nitro  and  Cyano  Derivatives. 

4.  Those  containing  sulphur.     Here  are  included  such 
compounds  as  the  Mercaptans  and  the  Sulphonic  Acids. 

205.  Substitution.  —  In  the  paraffin  series  the  carbon 
atoms  are  saturated,  i.e.  each  of  the  four  bonds  of  carbon 
holds  in  combination  an  atom  of  hydrogen.  This  may 
be  graphically  represented,  in  the  case  of  methane,  thus : 

H  H     H 

H  —  c  —  H.     Ethane  may  be  represented  thus :  H  —  C  —  C  —  H. 
I  I      I 

H  H     H 

H     H     H 

Propane  may  be  represented  thus  :  H  —  C  —  C  —  C  —  H.    Now, 

H    H    H 

since  the  carbon  atoms  can  hold  no  more  elements  in  com- 
bination, nothing  can  be  directly  added  to  any  of  the  hydro- 


INTRODUCTORY   TO   THE   CARBON   COMPOUNDS.        173 

carbons  of  the  paraffin  series.  But  when  any  one  of  these 
compounds  is  treated  with  the  proper  reagents,  one  or  more 
atoms  of  hydrogen  may  be  displaced,  and  another  element 
taken  instead.  Thus,  if  methane  be  mixed  with  chlorine 
gas,  and  then  exposed  to  the  action  of  diffused  sunlight, 
hydrochloric  acid  is  given  off,  and  different  products  are 
obtained,  depending  upon  the  duration  of  the  action.  Thus 
the  following  four  compounds  have  been  isolated,  by  re- 
placing the  hydrogen  in  methane,  CH4 :  chlor-methane, 
CH3C1;  dichlor-me thane,  CH2C12;  trichlor-methane,  CHC13; 
carbon  tetra-chloride  CC14. 

In  these  derivatives  it  is  plain  that  one  after  another  of 
the  hydrogen  atoms  has  been  displaced  by  chlorine.  The 
products  thus  obtained  are  called  Substitution  Products; 
and  the  process  of  substituting  other  atoms,  or  groups  of 
atoms,  for  hydrogen  is  termed  Substitution. 

Bromine  and  iodine  also  form  substitution  products  with 
methane. 

SUG.  Student,  write  the  formulae  of  these  products,  and  give  their 
names.  Thus,  CH3Br,  brom-methane ;  CH3I,  iodo-methane. 

Benzene,  C6H6,  of  the  benzene  series,  also  furnishes  a 
good  illustration  of  the  substitution  products:  C6H5C1, 
C6H4C12,  C6H3C13,  C6H2C14,  C6HC15,  C6C16. 

Sue.  Student,  name  these  compounds,  beginning  with  C6H3C1,  chlor- 
benzene.  Complete  the  series  of  substitution  products  for  benzene,  and 
give  the  names,  beginning  with  C6H5(N02),  nitro-benzene,  etc.,  etc. 

206.  Addition  Products.  —  In  the  case  of  the  olefine  series, 
other  elements  may  be  directly  added  to  the  hydrocar- 
bons. Ethylene  can  be  represented  by  the  graphic  for- 
mula, H2  =  C  =  C  :  -  H2,  in  which  the  carbon  atoms  are 
joined  by  two  bonds.  When  brought  under  the  influence 
of  the  proper  reagents,  it  seems  as  if  two  of  these  bonds 


174       INTRODUCTORY  TO   THE   CARBON   COMPOUNDS. 

are  released,  thus  enabling  this  hydrocarbon  to  act  like 
a  bivalent  radical.  Thus  we  have,  from  ethylene,  C2H4: 
ethylene  chloride,  C2H4012  ;  ethylene  bromide,  C2H4Br2 ; 
ethylene  hydrochloride,  C2H4HC1 ;  etc.  Other  series  also 
afford  examples  of  this  method  of  derivation.  Hydro- 
carbons that  form  addition  products  are  often  spoken  of 
as  unsaturated  compounds. 

207.  Unsaturated  Radicals  in  the  Paraffin  Series,  —  In  the 
paraffin  series  such  compounds  as  CH3C1,  CH3Br,  C2H5C1, 
C2H5Br,  etc.,  occur,  in  which  such  radicals  as  CH3  and 
C2H6  appear.     These  radicals  have  not  been  isolated,  but 
their  occurrence  is  so  common  that  they  have  been  assigned 
names  ending  in  "yl."     CH3  is  called  methyl,  and  C2H5  is 
called  ethyl.     These  radicals  have  one  atom  of  hydrogen 
less  than  the  primary  compounds  which  gave  them  origin. 
Thus :  — 

Methane,  CH4      .     .     .  Methyl,  CH3. 

Ethane,  C2H6  ....  Ethyl,  C2H5. 

Propane,  C3H8     .     .     .  Propyl,  C3H7. 

Butane,  C4H10.     .     .     .  Butyl,  C4H9. 
Etc.,  etc.  Etc.,  etc. 

All  these  radicals  are  monovalent,  and  they  act  like  univa- 
lent  metals  in  forming  salts.  Thus  we  have  methyl  chloride, 
CH3C1 ;  ethyl  bromide,  C2H5Br ;  propyl  iodide,  C3H7I ;  etc. 
Note  that  two  methods  of  naming  these  compounds  are  in 
use.  Thus  CH3C1  is  called  chlor-methane  or  methyl  chloride. 

Unsaturated  primary  compounds  like  the  defines  are 
sometimes  called  radicals. 

208,  Isomerism.  —  Frequently  one  formula  represents  two 
or  more  entirely  different  substances.    Each  compound  may 
contain  exactly  the  same  number  of  atoms  of  the  different 


INTRODUCTORY   TO   THE   CARBON    COMVOU.NDS.       175 


elements,  the  molecular  weights  may^fe^6=eSflieand  even 
the  vapor  densities  may  be  identical.  For  example,  C2H6O 
represents  two  entirely  different  substances.  One  is  methyl 
oxide,  (CH8)2O,  a  gas,  and  the  other  is  ordinary  alcohol,  or 
ethyl  hydroxide,  C2H5OH.  These  two  substances  fulfil  the 
foregoing  conditions  exactly,  and  are  called  Isomers.  When 
two  substances  afford  such  a  perfect  case  of  isomerism,  they 
are  also  called  Metameric  Isomers,  to  distinguish  them  from 
another  form  of  isomerism  in  which  the  molecular  weights 
of  the  different  compounds  vary  by  some  multiple  of  the 
lowest  member.  Thus  we  have  acetylene,  C2H2  ;  benzene, 
C6H6;  and  styrene,  C8H8.  These  substances  are  called 
Polymeric  Isomers.  The  CnH2n  series  of  hydrocarbons 
affords  good  examples  of  polymerism. 

209.  Uniformity  among  Derivatives.  —  Each  primary  hydro- 
carbon is  capable,  in  theory  at  least,  of  furnishing  a  set  of 
derivatives  similar  to  those  obtainable  from  any  other  hydro- 
carbon. Thus,  each  hydrocarbon  will  furnish  "a  set  of  halo- 
gen derivatives,  —  an  alcohol,  an  ether,  an  acid,  etc.,  etc. 
Hence  it  is  not  necessary,  in  order  to  obtain  a  general  view 
of  the  principles  involved  in  the  chemistry  of  the  carbon 
compounds,  to  study  all  the  hydrocarbons  and  their  deriva- 
tives in  detail.  The  study  of  any  one  hydrocarbon  series, 
such  as  the  paraffin  series,  would  answer  this  purpose. 

It  is  true  that  the  derivatives  obtained  even  from  hydro- 
carbons in  the  same  series  possess  different  physical  and 
chemical  characteristics,  but  it  is  also  true  that  they  pos- 
sess in  common  many  points  of  similarity.  As  a  rule,  with 
a  reasonable  number  of  exceptions,  the  general  reactions 
and  methods  employed  with  one  are  applicable  to  all. 

In  the  limited  space  at  our  disposal,  only  the  most  impor- 
tant compounds  can  be  considered. 


CHAPTER   XVI. 

THE   PARAFFIN    SERIES,    CnH2n4.2e 

210.  Occurrence  and  Preparation.  —  This  series  of  hydro- 
carbons is  often  called  the  marsh  gas  or  methane  series 
from  the  name  of  its  lowest  member.  Many  of  these 
primary  hydrocarbons  occur  in  crude  petroleum  and  in 
gases  occurring  in  connection  with  the  coal  deposits. 
Some  of  them,  as  well  as  some  of  their  derivatives,  are 
to  be  had  from  the  destructive  distillation  of  coal,  wood, 
bones,  and  the  refuse  liquids  or  "  vinasses  "  left  after  dis- 
tilling the  fermented  molasses  obtained  from  beet  sugar 
factories. 

As  a  matter  of  interest,  the  paraffin  series  can  be  built 
up  from  the  elements  by  synthetic  processes.  Thus,  when 
water  or  hydrogen  sulphide  is  mixed  with  carbon  disul- 
phide  (all  of  which  can  be  prepared  directly  from  the  ele- 
ments), and  the  mixture  passed  over  heated  metals,  such 
as  copper,  methane,  CH4,  the  first  member  is  obtained :  — 

CS2  4-  2  H20  +  6  Cu  =  CH4  +  2  Cu,S  +2  CuO. 

Now  by  treating  methane  with  iodine,  iodo-methane  or 
methyl  iodide,  CH3I,  is  to  be  had.  Then  when  methyl 
iodide  is  treated  with  metallic  sodium,  the  next  member, 
ethane,  C2H6,  is  produced :  — 

2  CH3I  +  2  Na  =  C2H6  +  2  Nal. 

Next  ethyl  iodide,  C2H5I,  can  be  prepared  from  ethane ; 
and  when  a  mixture  of  this  substance  and  methyl  iodide  is 

176 


PROPERTIES   OF  THE   PARAFFINS.  177 

treated  with  sodium,  the  next  member,  propane,  C8Hg,  is  to 

be  had:  — 

CH3I  +  C2H5I  +  2  Na  =  C3H8  +  2  Nal. 

Again,  when  ethyl  iodide  alone  is  treated  with  sodium, 
butane,  C4H10,  is  produced. 

2  C2H5I  +  2  Na  =  C4H10  +  2  Nal. 

It  can  be  readily  seen  that  in  this  way  it  is  possible  to 
build  up  a  large  number  of  the  members  of  this  series. 
Other  methods  of  synthesis  are  also  known  and  employed. 

Of  course  for  commercial  purposes  resort  is  usually  had 
to  the  natural  sources  of  the -different  compounds.  But 
such  synthetic  processes  are  of  interest  and  of  value,  since 
to  them  we  owe  much  of  our  knowledge  concerning  the 
constitution  of  the  carbon  compounds.  Moreover,  a  large 
range  of  possibilities  is  suggested  in  methods  of  building 
up  compounds,  which  have  of  late  borne  many  good  results, 
since  by  these  methods  various  substances  of  great  utility 
have  been  produced  by  artificial  means. 

211.  Properties  of  the  Paraffins.  —  Beginning  with  me- 
thane, a  gas,  this  series  gradually  passes  into  volatile 
liquids,  heavy  liquids,  and  finally  into  waxy  solids  at  ordi- 
nary temperatures.  It  is  from  these  solids,  the  paraffins, 
that  the  series  obtains  its  name.  Many  useful  and  well- 
known  substances  belong  to  this  series. 

Among  the  gases  is  methane,  or  fire  damp,  which  has 
already  been  described  under  carbon.  Ethane  and  propane 
are  also  gases.  Butane  is  a  liquid  boiling  at  1°  C.  Pen- 
tane  boils  at  38°  and  hexane  at  70°  C.  And  so  the  series 
passes  on  up  to  the  waxy  solids  known  as  "  paraffin,"  which 
is  a  mixture  of  the  higher  hydrocarbons  of  this  series. 

Petroleum,  or  rock  oil,  has  been  mentioned  as  one  of  the 


178  PROPERTIES   OF   THE   PARAFFINS. 

natural  sources  of  this  series.  From  this  crude  oil  are  ob- 
tained the  commercial  products,  cymogene,  rhigoline,  naph- 
tha, gasoline.,  kerosene,  lubricating  oil,  and  paraffin.  All  of 
these  products  are  mixtures  of  different  hydrocarbons. 

In  order  to  separate  these  substances  the  crude  oil  is 
subjected  to  distillation.  Beginning  with  low  temper- 
atures the  compounds,  ethane,  propane,  and  butane,  which 
were  dissolved  in  the  crude  oil,  pass  off  first  and  are 
condensed  under  pressure  to  a  liquid  consisting  principally 
of  butane.  This  liquid  is  known  as  cymogene,  and  is  used 
for  the  artificial  production  of  low  temperatures.  Products 
obtained  at  about  18°  F.  are  called  rhigoline.  From  this 
point  up  to  about  70°  F.  the  volatile  substances  known  as 
naphtha,  benzine,  gasoline,  etc.,  are  obtained.  These  are 
much  used  for  heating  and  illuminating  purposes,  but 
special  burners  are  required  for  their  consumption.  By 
means  of  a  rotary  air-pump  that  sends  a  current  of  air 
through  a  specially  appointed  tank  holding  gasoline,  a 
very  good  quality  of  gas  for  illuminating  and  heating  pur- 
poses is  obtained.  The  use  of  gasoline  in  our  modern 
gasoline  stoves  barely  needs  mentioning. 

Above  170°  F.  kerosene  oil  is  obtained,  while  at  still 
higher  temperatures  a  heavy  lubricating  oil  is  given  off. 
The  waxy  residue  is  purified  and  sold  under  the  name 
u  paraffin."  Vaselene,  or  cosmolene,  is  the  more  liquid 
portions  of  paraffin. 

The  kerosene  obtained  by  distillation  is  colored  and 
contains  objectionable  impurities.  Consequently  it  is 
subjected  to  refining  processes  in  which  it  is  treated  with 
sulphuric  acid,  alkalies,  and  water.  Thus  is  obtained 
the  water-white  oil  in  such  common  use  wherever  gas  is 
not  available. 

Kerosene  that  contains  the  more  volatile  hydrocarbons 


PROPERTIES   OF   THE   PARAFFINS. 


179 


is  dangerous  in  that  it  has  given  rise  to  many  disastrous 
conflagrations  by  exploding.  The  laws  of  nearly  all  coun- 
tries now  require  it  to  be  of  a  certain  standard,  which  varies 
somewhat  for  different  countries,  and  even  hi  different 
parts  of  the  same  country.  It  is  required  to  have  a  flash- 
ing-point, varying  from  73°  to  110°  F.,  according  to  the 
locality,  as  illustrated  in  the  following :  — 

EXP.  91.  Arrangfe  an  apparatus  as  shown  in  Fig.  34.  The 
glass  cylinder  A  has  a  wooden  cork  in  the  bottom,  and  the 
bent  glass  tube  d  terminates  in  a  fine 
jet  at  b.  A  large  eight-inch  test-tube 
having  its  bottom  removed  makes  a  good 
cylinder.  The  bottom  may  be  cut  off  by 
first  making  a  scratch  with  a  file,  and 
then  by  means  of  a  ten-penny  wire  nail 
heated  to  low  redness,  a  check  can  be 
started  at  the  file  mark  and  led  squarely 
around  the  tube. 

Fill  the  cylinder  about  one-third  full 
of  kerosene  to  be  tested,  and  then  place 
the  apparatus  in  a  water-bath  (a  tin  can 
will  answer)  up  to  the  level  of  the  kerosene.  Apply  heat  to  the 
bath,  and  force  a  steady  current  of  air  through  the  bent  tube 
until  there  is  a  half  an  inch  or  so  of  foam  on  the  kerosene. 
At  every  rise  of  one  degree  on  the  thermometer  apply  a 
lighted  taper  to  the  mouth  of  the  cylinder.  When  the  flame 
flashes  down  to  the  kerosene,  the  reading  of  the  thermometer 
gives  the  flashing-point. 

Asphalt  or  Asphaltum  is  a  solid  related  to  the  paraffins. 
It  occurs  in  vast  deposits,  as  at  Trinidad.  It  is  soluble  in 
turpentine  and  in  benzene,  and  is  used  as  a  paint,  etc. 

After  this  preliminary  view  of  the  paraffin  series  we  will 
next  consider  methane  and  ethane  and  some  of  their  most 
useful  derivatives. 


FIG.  34. 


180  METHANE   AND   ITS   DERIVATIVES. 

METHANE   AND    ITS    DERIVATIVES. 

I.    HALOGEN  DERIVATIVES. 

212,  Chlor-Methane,  or  Methyl  Chloride,  CH3C1,  —  Chlor- 
methane  has  already  been  noticed  as  the  first  substitution 
product  when   methane   and   chlorine   gas   react.      Pure 
methyl  chloride  is  prepared  by  treating  a  solution  of  zinc- 
methane,    Zn(CH3)2    (Art.    223),    and    methyl    alcohol, 
CH3OH  (Art.  215),  with  hydrochloric  acid. 

But  the  chlor-methane  of  commerce  is  now  largely  pre- 
pared from  the  destructive  distillation  products  of  the  beet 
root  vinasses.  Among  these  products  is  trimethylamine, 
N(CH3)3  (Art,  219).  This  is  treated  with  hydrochloric 
acid,  and  then  subjected  to  heat.  The  methyl  chloride 
thus  obtained  is  purified  by  treatment  with  hydrochloric 
acid,  and  then  dried  over  calcium  chloride.  It  is  then 
condensed  under  pressure  and  preserved  in  strong  cylin- 
ders. 

Methyl  chloride  is  a  mobile,  ethereal-smelling  liquid 
which  boils  at  23°.  It  is  now  much  used  in  making  various 
aniline  colors,  and  for  refrigerating  purposes.  It  burns 
with  a  green-bordered  flame. 

213,  Trichlor-Methane,  or  Chloroform,  CHC1S.  —  Of  the  re- 
maining chlorine  substitution  products  of  methane,  chlo- 
roform  is   the    only  one    deserving   mention   here.     The 
substituting  process  is  not  applicable  for  the  commercial 
production  of  chloroform.     In  commerce  several  processes 
are  employed. 

EXP.  92.  Place  a  few  crystals  of  chloral  hydrate, 
CC13.CH(OH)2,  in  a  test-tube,  add  a  concentrated  solution  of 
potassium  hydroxide,  KOH,  and  warm  gently.  Note  the  odor 


METHANE  AND  ITS   DERIVATIVES.  181 

of  the  chloroform  produced.     In  addition  to  the  chloroform 
potassium  formate  is  formed  :  — 

CC13.CH(OH)2  +  KOH  =  CHC13  +  CHK02  +  H20. 

Large  quantities  of  chloroform  are  manufactured  in  this 
way,  excepting  that  sodium  hydroxide  is  used  instead  of 
the  potassium  compound. 

Another  method  extensively  employed  is  to  treat  com- 
mon alcohol  with  bleaching-powder.  The  reactions  in- 
volved are  complicated,  and  cannot  well  be  represented 
by  one  equation. 

Chloroform  is  a  colorless,  mobile  liquid  which  possesses 
a  characteristic  and  penetrating  odor.  Its  specific  gravity 
is  1.525.  It  mixes  with  alcohol  and  ether,  but  not  with 
water.  It  acts  as  a  solvent  on  many  oils,  gums,  resins, 
and  alkaloids.  Hence  it  is  much  used  in  the  arts  and  for 
analytical  purposes. 

Chloroform  is  extensively  used  in  medicine  and  in  sur- 
gery as  an  anaesthetic. 

214.  Tri-iodo-Methane,  or  lodofonn,  CHI3.  —  lodoform  is  a 
yellowish  solid  which  crystallizes  in  six-sided  plates.  This 
is  the  most  important  of  the  iodine  substitution  products 
of  methane.  It  can  be  prepared  by  the  action  of  iodine  on 
ethyl  alcohol,  in  the  pressure  of  an  alkali,  or  an  alkaline 
carbonate. 

EXP.  93.  Dissolve  106  crystallized  sodium  carbonate  in 
50CC  water,  add  about  6CC  common  alcohol,  and  warm  up  to 
about  70°  C.  Now  slowly  add  5g  iodine  and  agitate.  Note 
the  crystals  of  iodoform  that  separate  out.  Eemove  the  crys- 
tals by  filtration ;  dry  them  between  pieces  of  blotting-paper. 
Xote  their  odor  and  their  other  characteristics. 

The  preceding  experiment  illustrates  the  commercial 
processes  involved  in  the  manufacture  of  iodoform,  but 


182  METHANE   AND   ITS   DERIVATIVES. 

some  of  the  by-products  obtained  along  with  the  iodoform 
are  so  treated  that  a  part  of  them  is  also  converted  into 
iodoform.  Other  materials  and  processes  are  also  em- 
ployed. If  we  use  potassium  hydroxide  instead  of  the 
sodium  carbonate,  the  principal  reactions  may  be  repre- 
sented thus :  — 

CH3.CH2OH  +  4 12  +  6  KOH  =  CHI3  +  CHK02  +  5  KI  +  5  H20. 

Iodoform  has  an  odor  resembling  saffron ;  it  is  insoluble 
in  water,  but  soluble  in  alcohol.  It  is  used  in  medicine 
and  in  surgery.  It  has  an  anaesthetic  action,  especially 
upon  the  muscles,  even  when  applied  locally. 

II.    OXYGEN  DERIVATIVES. 

215,  Methyl  Alcohol,  or  Wood  Alcohol,  CH3OH.  —  This 
compound  is  an  important  one  both  from  a  theoretical 
and  from  a  practical  standpoint.  In  the  first  place,  it  is  a 
type  of  a  number  of  alcohols,  and  bears  the  same  relation 
to  methane  that  any  other  primary  alcohol  does  to  the 
hydrocarbon  from  which  it  is  derived.  An  alcohol  is  a 
hydroxide  of  a  primary  hydrocarbon  obtained  by  replacing 
one  atom  of  hydrogen  by  the  radical  hydroxyl,  OH.  Thus 
methane,  CH4,  or  CH3H,  yields  methyl  alcohol  CH3OH. 

Methyl  alcohol  does  not  occur  free  in  nature,  but  one  of 
its  salts,  methyl  salicylate,  CH8C7H5O3,  occurs  ready  formed 
in  the  oil  of  wintergreen,  Graultheria  procumbent 

The  principal  method  of  obtaining  this  alcohol  is  the 
recovery  of  the  alcohol  produced  by  the  dry  distillation  of 
wood  and  of  beet  root  vinasses.  Other  products,  such  as 
tarry  substances  and  acetic  acid,  are  obtained  at  the  same 
time.  These  mixtures  are  first  distilled,  when  what  little 
methyl  alcohol  is  present  is  found  in  the  first  portions  of 


METHANE   AND    ITS    DERIVATIVES.  183 

the  distillate.  The  crude  spirit  is  next  treated  with  quick- 
lime, caustic  soda,  and  a  weak  oxidizing  reagent  in  order 
to  destroy  some  of  the  accompanying  impurities.  Next  it 
is  subjected  to  a  systematic  course  of  fractional  distillation 
(see  Art.  225),  when  the  wood  alcohol  of  commerce  is 
obtained. 

In  order  to  obtain  pure  methyl  alcohol,  the  commercial 
article  is  treated  with  oxalic  acid,  which  produces  the  solid 
substance  methyl  oxalate,  (CH3)2C2O4.  This  compound 
when  treated  with  water  yields  the  pure  spirit  and  oxalic 
acid. 

Methyl  alcohol  can  be  built  up  by  synthetical  reactions, 
but  these  are  of  scientific  interest  only. 

This  alcohol  is  a  mobile  liquid  of  a  pleasant,  vinous  odor, 
and  it  finds  employment  for  many  mechanical  purposes,  and 
for  preparing  the  aniline  colors. 

216.  Methyl  Ether,  (CH3)20.  —  This  compound  is  also  a 
type  of  an  important  class  of  substances,  the  ethers.  A 
simple  ether  is  really  an  oxide  of  an  unsaturated  radical, 
such  as  methyl,  CH3 ;  ethyl,  C2H5 ;  etc.  These  ethers 
may  be  considered  as  derived  from  alcohols  by  replacing 
the  hydrogen  of  hydroxyl  by  the  alcohol  radical.  Thus 
from  methyl  alcohol,  CH3— O— H,  we  get  methyl  ether, 
CH3-O-CH3. 

In  practice,  methyl  ether  is  obtained  by  acting  on  methyl 
alcohol  by  strong  sulphuric  acid.  A  mixture  of  these  sub- 
stances is  made  of  the  specific  gravity  1.29.  This  mixture 
is  heated  from  125°  to  128°,  and  never  above  130°,  when 
the  ether  is  regularly  given  off.  The  process  is  made  con- 
tinuous by  adding  enough  of  the  alcohol  from  time  to 
time  to  bring  the  mixture  back  to  the  required  specific 
gravity. 


184  METHANE   AND   ITS   DEBIT  ATI  VES. 

Methyl  ether  is  a  gas  having  a  pleasant  odor.  It  is  con- 
densed to  a  liquid  by  means  of  pressure,  and  used  in  large 
quantities  for  refrigerating  purposes. 

217.  Methyl  Aldehyde,  or  Formic  Aldehyde,  CH20.  —  This 
substance  is  also  typical  of  a  class  of  compounds  yielded 
by  each  hydrocarbon.     An  aldehyde  is  obtained  by  gently 
oxidizing  an  alcohol.     When  vapors  of  methyl  alcohol  and 
air  are  brought  in  contact  with  a  glowing  platinum  spiral, 
the  following  reaction  occurs :  — 

CH3OH  +  0  =  CH20  +  H20. 

Methyl  aldehyde  has  a  peculiar  and  penetrating  odor. 
It  has  been  prepared  in  dilute  solutions  only. 

218.  Formic  Acid,  CH202.  —  When  the  oxidation  of  me- 
thyl alcohol  is  carried  farther  than  in  the  case  of  methyl 
aldehyde,  two  atoms  of  hydrogen  are  withdrawn  from  each 
molecule  of  the  alcohol,  and  formic  acid  is  produced :  — 

CH3OH  +  20  =  CH202  +  H20. 

Each  primary  alcohol  has  a  corresponding  acid. 

This  acid  occurs  ready  formed  in  the  bodies  of  red  ants, 
in  stinging  nettles,  in  tamarinds,  and  in  the  shoots  of  vari- 
ous pines. 

It  may  be  prepared  in  many  ways  as  by  the  distillation 
and  oxidation  of  various  organic  substances.    But  it  is  now 
principally  obtained  by  heating  oxalic  acid :  — 
C2H204  =  CH202  +  CO., 

In  practice,  the  acid  is  mixed  with  anhydrous  glycerine, 
and  the  details  are  so  arranged  that  the  process  becomes 
continuous.  The  reactions  are  somewhat  complicated. 

This  acid  is  a  colorless  liquid  which  emits  fumes  of  a 
penetrating  acid  odor.  It  acts  so  violently  on  the  skin 


METHANE   AND   ITS   DERIVATIVES.  185 

that  one  or  two  drops  produce  extreme  pain  and  leave 
painful  white  blisters.  With  the  metals  it  forms  a  series 
of  salts,  the  formates,  in  which  it  plays  the  part  of  an  ordi- 
nary monobasic  acid. 

III.    NITROGEN  DERIVATIVES. 
1.    Substituted  Ammonias,  or  Amines. 

219,  The  Methylamines.  —  Ammonia  can  be  made  to  give 
up  one,  two,  or  three  of  its  hydrogen  atoms  and  take  in 
place  thereof  one,  two,  or  three  unsaturated  hydrocarbon 
radicals.  Thus  we  have  ammonia,  NH3;  methylamine, 
NELjCH-j1;  dimethylamine,  NH(CH3)2;  and  trimethy la- 
mine,  N(CH3)3.  These  compounds  are  called  amines,  and 
many  such  are  known  corresponding  to  other  radicals 
besides  methyl. 

The  amines  have  a  strong  ammoniacal  smell  which  is 
usually  accompanied  by  a  fishy  odor.  Like  ammonia  they 
unite  with  acids  without  replacing  the  hydrogen  of  the 
acids.  Thus :  NH2CH3  +  HC1  =  NH2CH3 .  HC1,  or  methyl- 
amine hydrochloride. 

The  methylamines  occur  in  small  quantities  in  nature. 
They  are  all  produced  by  the  distillation  of  wood. 

Methylamine,  NH2CH3,  occurs  in  herring  brine.  Dimeth- 
ylamine, NH(CH3)2,  occurs  in  Peruvian  guano.  Trimeth- 
ylamine,  N(CH3)3,  occurs  quite  widely  distributed.  It  is 
found  in  various  plants,  and  in  the  bloom  of  the  pear, 
wild-cherry,  and  hawthorn.  It  also  occurs  in  herring 
brine.  It  is  now  prepared  in  large  quantities  by  distill- 
ing beet  root  vinasses.  It  is  employed  for  manufacturing 

1  The  hypothetical  radical,  NH2,  is  often  called  amidogen,  and  the 
compounds  in  which  it  occurs  are  termed  the  awitZo-compounds. 


186  METHANE    AND   ITS   DERIVATIVES. 

potassium  carbonate,  just  as  ammonia  is  used  for  making 
sodium  carbonate.  The  methylamines  can  be  prepared  by 
synthetic  processes  which  are  of  minor  interest  to  the 
beginner. 

2.    The  Cyano-Derivatives. 

220,  Cyanogen,  CN,  and   Hydrocyanic   Acid,   HCN,   have 
been  noticed  under  Arts.  8T  and  88.     The   hydrocarbon 
radicals  unite  with  hydrocyanic  acid  to  form  the  cyanides 
or   Nitrils ;    e.g.  methyl    cyanide   or  aceto-nitril,  CH3CN. 
There  is  another  class  of   compounds   isomeric  with  the 
cyanides  which  have  received  the  distinguishing  names  of 
the  Isocyanides  or  the  Carbamines  ;  e.g.  methyl  carbamine, 
CH3NC. 

There  is  also  a  hypothetical  cyanic  acid,  CNOH,  which 
gives  rise  to  the  cyanates  and  an  isomeric  acid  yielding  the 
isocyanates,  or,  as  they  are  frequently  called,  the  Carba- 
mides  or  the  Carbonylamines. 

Ammonium  cyanate,  NH4NCO,  is  of  interest,  since  when 
heated  it  undergoes  a  rearrangement  of  its  atoms,  and  is 
converted  into  Urea  or  Carbamide.  This  substance  is  a 
white  solid  occurring  in  many  animal  fluids.  It  is  the 
first  so-called  organic  compound  prepared  by  synthesis. 

There  is  a  remarkable  tendency  among  the  cyanogen 
compounds  to  polymerize,  in  consequence  of  which  the 
number  of  these  compounds  is  very  great.  Thus  we  have 
H3C3N3,  a  solid  called  trihydrocyanic  acid,  a  polymer  of 
HCN,  hydrocyanic  acid.  Again,  cyanic  acid  has  the 
polymer,  cyanuric  acid,  C3N3O3H3. 

3.    The  Nitre-Derivatives. 

221.  Nitre-Methane,  CH3N02.  —  The  radical  NO2  unites 
with   methyl,  ethyl,  etc.,   to   form   the    nitro-compounds. 


METHANE   AND   ITS   DERIVATIVES.  187 

Nitre-methane  is  to  be  had  by  a  variety  of  reactions,  e.g. 
by  the  action  of  methyl  iodide  on  silver  nitrite :  — 

CH3I  +  AgN02  =  CH3N02  +  Agl. 

It  is  a  heavy  liquid  having  a  characteristic  odor.  When 
heated  with  fuming  sulphuric  acid,  carbon  monoxide  and 
Hydroxylamine  are  produced :  — 

CH3N02  =  NH2OH  +  CO. 

It  acts  like  a  weak  acid  in  uniting  with  bases  to  form 
salts.  These  salts  are  violently  explosive. 

The  radical  NO  can  displace  hydrogen  from  the  hydro- 
carbons to  form  the  Nitroso  and  the  Isonitroso  compounds. 
Fulminic  acid,  C2N2O2H2,  forms,  as  an  example  of  the  iso- 
nitroso  compounds,  C2N2O2Hg,  which  is  commonly  called 
fulminating  mercury.  A  mixture  of  this  salt  and  potas- 
sium nitrate  is  used  as  the  fulminating  powder  in  gun- 
caps.  Fulminating  mercury  is  prepared  by  dissolving 
mercury  in  strong  nitric  acid;  then  alcohol  is  added  to 
the  solution. 

iy.    DERIVATIVES  WITH  SULPHUR,  ARSENIC, 
PHOSPHORUS,  ETC. 

222.  The  Mercaptans,  Phosphines,  Arsines,  and  Stibines. 
—  With  hydrogen  sulphide,  methyl,  ethyl,  etc.,  form  a 
class  of  compounds  called  the  mercaptans.  Methyl  mer- 
captan,  CH3SH,  is  obtained  by  treating  potassium  acid 
sulphide  with  methyl  iodide  :  — 

CH3I  +  HKS  =  CH3SH  +  KL 

Methyl  mercaptan  is  a  liquid  of  an  extremely  disagree- 
able odor.  All  the  mercaptans  likewise  are  disagreeable- 
smelling  compounds. 


188  METHANE   AND    ITS   DERIVATIVES. 

Both  hydrogen  atoms  in  hydrogen  sulphide  may  be  re- 
placed by  hydrocarbon  radicals,  thus  giving  rise  to  a  class 
of  compounds  that  are  comparable  to  the  ethers.  Thus 
we  have  methyl  sulphide,  (CH3)2S ;  ethyl  sulphide, 
(C2H5)2S ;  etc.  These  compounds  are  liquids  of  disagree- 
able odors. 

By  the  oxidation  of  a  mercaptan,  an  acid  called  a  Sul- 
phonic Acid  is  obtained.  Methyl  sulphonic  acid,  CH3HSO3. 
and  ethyl  sulphonic  acid,  C2H5HSO3,  will  serve  as  exam- 
ples. These  acids  may  be  regarded  as  derived  from  sul- 
phuric acid  by  replacing  one  hydroxyl  by  a  radical.  Thus, 
OHHSO3,  sulphuric  acid,  gives  CH3HSO3,  methyl  sul- 
phonic acid. 

The  sulphonic  acids  form  salts  with  bases.  As  an  ex- 
ample, methyl  potassium  sulphonate,  CH3KSO3,  may  be 
cited. 

Phosphine,  PH3,  Arsine,  AsH3,  and  Stibine,  SbH3,  may 
have  one  or  more  of  their  hydrogens  replaced  by  a  hydro- 
carbon radical  to  form  the  PJiosphines,  Arsines,  and  the 
Stibines.  The  arsine  compounds  are  often  called  the 
Oacodyl  compounds  on  account  of  their  evil  odors. 

SUG.  Student,  write  and  name  the  methyl  phosphines,  arsiiies,  and 
stibines. 

V.     METALLIC  DERIVATIVES. 

223.  A  few  of  the  metals  combine  with  the  hydrocarbon 
radicals  to  form  liquid  compounds  that  are  mostly  vola- 
tile. Lead,  tin,  mercury,  aluminum,  and  zinc  are  among 
the  metals  forming  such  compounds.  Zinc  methyl, 
Zn(CH3)2,  and  zinc  ethyl,  Zn(C2H5)2,  will  serve  as  exam- 
ples in  which  it  will  appear  that  the  usual  laws  of  valence 
hold  good.  There  are  a  few  exceptional  compounds  of 
little  importance. 


OXYGEN    DERIVATIVES.  189 

The  list  of  the  methyl  compounds  considered  in  the 
preceding  paragraphs  is  by  no  means  exhaustive  ;  but  a 
sufficient  number  has  been  given  to  show  the  general 
characteristics  of  the  methane  derivatives.  Since  the 
derivatives  of  the  other  paraffin  hydrocarbons  arrange 
themselves  in  similar  groups,  we  may  next  proceed  to 
the  ethane  derivatives,  neglecting  all  but  those  -of  the 
most  importance. 

ETHANE   AND    ITS    DERIVATIVES. 


224.  Ethane,  C^.  —  Ethane  is  a  colorless,  odorless  gas 
that  burns  with  a  faintly  luminous  flame.  It  occurs  dis- 
solved in  petroleum,  and  mixed  with  the  gases  issuing 
from  gas-wells. 

It  can  be  prepared  in  many  ways,  one  of  which  has  been 
mentioned.  When  potassium  acetate  is  subjected  to  elec- 
trolysis in  suitable  apparatus,  ethane  is  produced  together 
with  some  other  substances  that  may  be  removed  by  wash- 
ing through  bulbs  containing  potassium  hydroxide  and 
sulphuric  acid.  It  is  also  easily  prepared  by  treating 
mercuric  ethyl  with  sulphuric  acid  :  — 

2  Hg(C2H5)2  +  H2S04  =  2  C2H6  +  (C2H5Hg)2S04. 

Ethane  has  no  practical  application  in  the  arts,  and 
since  its  halogen  derivatives  resemble  those  of  methane, 
we  may  proceed  immediately  to  the 

OXYGEN   DERIVATIVES. 


225.  Ethyl  Alcohol,  C^OE  or  CsHeO.—  This  alcohol  is 
the  best  known  of  all  the  alcohols.  It  is  usually  called 
simply  "  alcohol  "  or  spirits  of  wine.  It  occurs  in  nature 


" 


190 


OXYGEN   DERIVATIVES. 


widely  distributed  throughout  the  vegetable  kingdom,  but 
in  small  quantities. 

Owing  to  the  enormous  quantities  consumed  in  different 
ways  its  artificial  production  is  now  one  of  the  industries 
of  the  age.  It  can  be  built  up  synthetically,  but  for 
commerce  it  is  always  produced  by  the  action  of  ferments 
on  such  substances  as  starch  and  the  sugars. 

EXP.  94.  Place  in  a  large  bottle  about  I1  of  a  dilute 
solution  of  grape  sugar  or  of  molasses.  Add  a  little  baker's 
yeast  and  fit  a  cork  carrying  a  bent  delivery-tube  which  dips 
down  into  a  test-tube  containing  a  solution  of  calcium  hydrox- 
ide. Place  the  bottle  in  a  moderately  warm  place  and  allow  it 


FIG.  35. 

to  stand  until  carbon  dioxide  ceases  to  come  off  (note  the  cal- 
cium hydroxide  solution  from  time  to  time).  When  fermen- 
tation has  ceased,  place  the  contents  of  the  bottle  in  the 
distilling-flask  of  an  apparatus  arranged  as  in  Fig.  35.  Distil 


OXYGEN  DERIVATIVES.  191 

until  about  100CC  of  the  distillate  is  collected  in  the  receiver. 
The  reaction  for  cane  sugar  is  :  — 


Test  the  distillate  for  alcohol  by  the  odor  and  by  the  iodof  orm 
reaction  thus  :  Warm  a  small  portion  of  the  liquid  in  a  test- 
tube,  and  add  a  few  crystals  of  iodine.  Then  add  sufficient 
potassium  hydroxide  to  decolorize  the  solution.  ]N"ow  allow  the 
contents  of  the  tube  to  cool,  when  yellow  crystals  of  iodof  orm 
will  be  deposited. 

In  order  to  obtain  the  alcohol  in  a  state  of  greater  purity, 
the  distillate  may  be  treated  by  a  process  termed  Frac- 
tional Distillation. 

EXP.  95..  Place  the  distillate  just  obtained  in  a  smaller 
flask  and  connect  it  to  the  same  condensing  apparatus  used 
before.  Maintain  a  temperature  by  means  of  the  thermometer 
B  of  about  80°  to  90°,  until  half  the  liquid  has  distilled  over. 
Eeject  what  remains  in  the  flask,  return  the  distillate  to  the 
flask,  and  distil  off  about  one-half  once  more.  Xow  note  that 
the  distillate  is  stronger  in  alcohol  than  any  portion  previ- 
ously obtained. 

This  process  is  much  employed  in  separating  liquids 
which  boil  at  different  temperatures. 

In  the  commercial  preparation  of  alcohol,  grains,  fruits, 
potatoes,  and  rice  are  employed.  After  the  substance  em- 
ployed has  fermented,  the  alcohol  is  separated,  to  a  great 
extent,  from  its  accompanying  impurities  in  its  water  solu- 
tion in  huge  stills  which  are  so  arranged  that  the  water  is 
mostly  condensed  and  allowed  to  flow  back  while  the  alco- 
holic vapors  pass  on  and  are  condensed  in  other  portions 
of  the  apparatus.  But  the  commercial  alcohol  thus  ob- 
tained is  not  pure.  It  contains  some  water  and  a  mixture 
of  the  higher  alcohols  wiiich  is  termed  fusel  oil.  These 
can  be  further  removed  by  fractionation  and  by  filtering 


192  OXYGEN   DERIVATIVES. 

through  boneblack.  Some  water  still  remains,  which  is 
mostly  removed  by  treatment  with  quicklime  or  other 
hygroscopic  agents,  after  which  it  is  again  distilled.  Fi- 
nally the  insignificant  portion  of  water  that  still  remains  is 
removed  by  means  of  metallic  sodium,  and  a  final  distilla- 
tion. In  this  way  Absolute  Alcohol  is  prepared. 

Ethyl  alcohol  is  the  intoxicating  principle  found  in  such 
beverages  as  whiskey,  brandy,  gin,  rum,  wine,  beer,  and 
cider.  These  substances  vary  in  their  alcoholic  content 
and  in  other  respects.  While  there  is  no  uniformity,  the 
first  four  contain  from  25  to  50  or  even  55  per  cent,  and 
the  last  three  from  5  to  20  per  cent  of  alcohol.  The  dif- 
ferences of  taste  and  odor  are  due  to  the  materials  from 
which  they  are  prepared.  It  seems  that  each  substance 
gives  rise  to  certain  peculiar  ethereal  essences  and  other 
ingredients  which  imparts  to  the  liquor  manufactured 
from  it  a  distinctive  flavor. 

Ex.  State  from  what  substances  each  of  the  beverages  just  mentioned 
is  produced. 

Pure  alcohol  is  a  limpid  liquid  of  a  pleasant  and  slightly 
ethereal  odor.  It  mixes  with  water  with  great  avidity  in 
all  proportions.  It  boils  at  78.3°  and  has  been  frozen  at 
- 130.5°. 

Ex.     Name  the  uses  of  commercial  alcohol. 

It  has  been  stated  that,  corresponding  to  each  primary 
hydrocarbon,  there  is,  in  theory  at  least,  a  primary  alcohol. 
A  list  of  these  primary  alcohols,  so  far  as  known,  for  the 
paraffin  series,  is  given  in  Art.  228. 

But  if  we  begin  with  propyl  alcohol,  C3H8O,  there  are 
some  isomeric  alcohols,  called  secondary  alcohols,  in  addi- 
tion to  the  primary  alcohols,  for  some  of  the  remaining 
paraffin  hydrocarbons.  These  isomers  may  be  considered 


OXYGEN   DERIVATIVES.  193 

as  derived  from  methyl  alcohol  by  the  replacement  of  two 
hydrogens  by  an  alcohol  radical.  Thus,  if  we  represent 

I  H 
methyl   alcohol   by   C  j    ^  ,   we   can   represent   secondary 

I  OH 

fCH, 

pTT 

propyl  alcohol  by  C  i       3.     Also,  if  we  call  methyl  alco- 

1  OH 

hoi  by  the  name  "  carbinol "  as  has  been  proposed,  we 
can  name  secondary  propyl  alcohol  "dimethyl  carbinol." 
The  following  list  gives  the  secondary  alcohols  of  the 
paraffins :  — 

LIST  OF  SECONDARY  ALCOHOLS. 

Boiling-point. 
•S  r  1 1  \-\ 

Secondary  propyl  alcohol 

or   *  ^C3H80  =  C^   ~;7  .     .       84°. 

.      Dimethyl  carbinol 

Secondary  butyl  alcohol 

or  }  C4H10O  =  C  \    ~;7°  .     .       97°. 

Methyl-ethyl-carbinol 

Secondary  amyl   alcohol 

or  J>C5H120  =  CM   ~3TV.     .     108°. 

Methyl-propyl-carbinol 

Secondary  hexyl  alcohol 

CYV  V    P    ~H  —  P    -I       ^*^*~9  1  Q£0 

f-  \j6nu\J  =  O  \      TT     .      .      loo  . 

Methyl-butyl-carbinol 

iBecondary  octyl   alcohol 

nr  v  r1  P   n  _  r  1  ^6iAis          -10-10 

f  L-xrl^U  =  \j  \       TT     .       .       lol  . 

Methyl-hexyl-carbinol      ,  , 


194  OXYGEN   DERIVATIVES. 

Beginning  with  butyl  alcohol  there  is,  in  addition  to  the 
two  classes  of  alcohols  already  described,  a  third  class, 
called  tertiary  alcohols,  made  by  replacing  three  hydro- 
gens from  methyl  alcohol,  with  alcohol  radicals. 

LIST  OF  TERTIARY  ALCOHOLS. 

Boiling-point. 

Tertiary    butyl     alcohol  "1  {  //nTT  N 

I  r  TT  n      n  J  W^a          coo 
>  C4H10O       j  <  QH 

Trimethyl-carbinol 

Tertiary     amyl     alcohol  1  f  (CH3)2 

or  >  C5H120  =  C  <  C2H5 .     .     100°. 

Dimethyl-ethyl-carbinol  J  I  OH 

Tertiary  hexyl  alcohol    1  f  (CH3)2 

or  f  C6H140  =  C<!  C3H7       .     120°. 

Dimethyl-propyl-carbinol  J  I  OH 

Methyl-diethyl    methane  ]  f  CH3 

or  VC6H140  =  C^  (C2H5)2.     115°: 

Methyl-diethyl-carbinol    J  I  OH 

Tertiary   heptyl    alcohol  ~] 

[dUIkO 
Triethyl  carbinol 

Tertiary     octyl     alcohol  1 

or  ^C8H180 

Diethyl-propyl-carbinol    . 

226.  Ethyl  Ether,  (C2H5)20.  —  This  is  commonly  known 
simply  as  "ether."  It  is  the  best  known  of  any  of  the 
substances  in  the  class  to  which  it  belongs.  Ether  is  pre- 
pared for  commerce  by  the  action  of  sulphuric  acid  on 
ethyl  alcohol. 

EXP.  96.  Fit  a  flask  with  a  cork  containing  three  holes. 
In  one  hole  place  a  delivery -tube,  in  the  second  a  thermometer, 


OXYGEN   DERIVATIVES.  195 

and  in  the  third  a  funnel-tube.  Place  in  the  flask  a  mixture 
of  alcohol  (90  per  cent),  five  parts,  and  concentrated  sulphuric 
acid,  nine  parts.  Insert  the  cork,  allowing  the  thermometer 
and  the  funnel-tube  to  dip  below  the  liquid.  Now  join  the 
delivery -tube  to  a  condenser,  and  heat  the  mixture  up  to  the 
boiling-point,  which  should  be  about  140°.  Allow  alcohol  tc 
enter  the  funnel-tube,  drop  by  drop,  while  the  liquid  is  boiling. 
When  about  25CC  of  distillate  have  collected  in  the  condenser, 
the  operation  may  be  brought  to  a  close.  Place  the  distillate 
in  a  large  test-tube,  add  water,  and  shake.  Note  the  layer  of 
ether  which  collects  above  the  water.  Note  its  odor,  and  be 
careful  not  to  bring  it  near  a  flame.  Pour  a  few  drops  on  the 
hand,  and  allow  it  to  evaporate. 

The  reactions  take  place  in  two  stages.  At  first  ethyl 
sulphuric  acid  is  formed :  — 

C2H5OH  +  H2S04  =  C2H5HS04  +  H20. 

Then  another  molecule  of  alcohol  and  this  ethyl  sulphuric 
acid  react  to  form  ether  and  sulphuric  acid :  — 

C2H5HS04  +  C2H5OH  =  (C2H6)20  +  H2S04. 
This  sulphuric  acid  is  now  ready  to  act  upon  another  mol- 
ecule of  alcohol  to  form  ethyl  sulphuric  acid  again,  which 
in  turn  may  once  more  react  with  another  molecule  of 
alcohol  to  form  more  ether.  Thus  the  process  becomes 
continuous,  and,  in  theory,  a  small  quantity  of  sulphuric 
acid  may  form  an  unlimited  amount  of  ether ;  but  in 
practice,  the  acid  after  a  while  becomes  too  dilute,  and 
the  reaction  ceases. 

Ether  is  an  extremely  mobile,  inflammable  liquid, 
which  boils  at  34.9°,  and  at  0°  has  a  specific  gravity  of 
0.73568. 

Ether  has  many  uses.  In  the  laboratory  and  in  the  arts 
and  manufactures  it  is  used  as  a  solvent.  It  is  also  used 
in  manufacturing  ice ;  and  in  medicine  it  is  used  as  an 


196  OXYGEN   DERIVATIVES. 

ansesthetic.     Its  action  upon  the  system  is  similar  to  that 
of  laughing-gas. 

227.  Ethyl  Aldehyde,   C2H40.  —  This   substance   is   also 
known    as    acetaldehyde,   since    by   further   oxidation   it 
passes   into   acetic    acid.      It    is    a    liquid   which    has    a 
peculiar  ethereal,  but   suffocating   odor.      When   inhaled 
in  quantities,  it  acts  violently  upon  the  system. 

EXP.  97.  To  a  solution  of  potassium  bichromate,  in  a  test- 
tube,  add  sulphuric  acid  until  the  solution  becomes  dark  red. 
Then  add  a  small  quantity  of  alcohol.  Note  the  odor,  which  is 
that  of  "  aldehyde,"  as  the  ethyl  aldehyde  is  commonly  called. 

Aldehyde  is  used  in  the  arts  for  the  preparation  of  alde- 
hyde green,  one  of  the  so-called  aniline  colors.  Commer- 
cial aldehyde  is  a  by-product  obtained  in  the  manufacture 
of  alcohol. 

Aldehyde  is  capable  of  yielding  substitution  products, 
one  of  which  is  known  as  Chloral,  C2HC13O.  Chloral  may 
be  regarded  as  aldehyde  in  which  three  atoms  of  hydrogen 
have  been  displaced  by  chlorine.  It  is  a  colorless  liquid, 
which  unites  with  water  to  form  the  valuable  medicine, 
Chloral  Hydrate,  C2HC13O.H2O.  In  practice,  chloral  is 
obtained  by  treating  absolute  alcohol  with  chlorine  for 
six  or  eight  weeks,  after  which  the  solution  is  kept  in 
contact  with  sulphuric  acid  until  the  chloral  separates  out. 
After  purification,  the  requisite  amount  of  water  is  added 
to  produce  the  hydrate.  This  hydrate  is  used  as  an  anaes- 
thetic and  an  hypnotic. 

228.  Acetic  Acid,  C2H402  or  HC2H302.  —  Acetic  acid  is  one 
of  the  most  valuable  of  the  organic  acids.     In  weak  and 
impure  solutions  it  is  known  as  Vinegar.      When  fruit 
juices,  such  as  those  of  the  apple  and  grape,  are  kept  at 


OXYGEN  DERIVATIVES. 


197 


the  proper  temperature,  alcoholic  fermentation  first  sets  in. 
The  weak  solution  of  alcohol  thus  obtained,  under  the 
proper  conditions  undergoes  another  kind  of  fermentation, 
known  as  acetous  fermentation.  This  latter  action  is  due 
to  the  presence  of  a  microscopic  organism,  Mycoderma  aceti, 
commonly  called  "  mother  of  vinegar."  Hence  it  appears 
that  the  acetic  acid  of  vinegar 
is  really  an  oxidation  product 
of  alcohol.  Vinegar  is  now  pre- 
pared, on  the  large  scale,  by 
allowing  weak  alcoholic  solu- 
tions to  trickle  slowly  through 
wooden  casks  filled  with  shav- 
ings. The  rapidity  of  the  action 
is  greater  when  some  mother  of 
vinegar  is  present. 

The  source  of  the  pure  acetic 
acid  used  in  the  laboratory  is 
the  crude  acetic  or  pyroligneous  acid  obtained  in  distill- 
ing wrood.  A  metallic  salt  of  acetic  acid  is  first  prepared 
and  purified.  Then  this  salt  is  treated  with  sulphuric  acid, 
and  distilled.  The  acetic  acid  thus  obtained  is  freed  from 
water  by  distillation,  thus  giving  G-laeial  Acetic  Acid. 

Acetic  acid  is  a  stable  monobasic  acid  which  yields  a 
well-known  series  of  salts,  —  the  acetates.  It  also  yields 
a  series  of  substitution  products.  Thus  acetyl  chloride, 
C2H3OC1,  is  used  as  a  reagent  in  the  laboratory. 

When  an  acetate  is  subjected  to  distillation,  a  substance 
known  as  Acetone,  C3H6O,  is  obtained:  — 

Ca(C2HA)2  =  C3H60  +  CaC03. 

Acetone  is  a  substance  closely  allied  to  aldehyde,  and  is  a 
representative  of  a  class  of  compounds  called  the  Ketones. 


FIG.  36. 


198 


OXYGEN  DERIVATIVES. 


We  have  now  studied  methyl  and  ethyl  alcohols,  and 
formic  and  acetic  acids.  These  are  the  most  important 
substances  of  their  classes,  derived  from  the  paraffins,  and 
space  forbids  notice  of  the  less  important  compounds  of  a 
similar  nature.  But  the  following  table  gives  a  list  of  the 
primary  alcohols  of  the  methane  series,  together  with  their 
corresponding  acids :  — 


PRIMARY  ALCOHOLS, 
General  formula,  CnH2M+20, 


yield 


f 


FATTY  Acios,1 


(  General  formula,  CMH2n02. 


Name. 

Formula. 

Boiling- 
Point. 

Name. 

Formula. 

Boiling. 
Point. 

Melting- 
Point. 

Methyl  .  .  . 

C  H40 

66°  C. 

Formic.   .  . 

C  H202 

100° 

1° 

Ethyl  .... 

C2H60 

78°.4 

Acetic  .  .  . 

C2  H4  02 

118° 

17° 

Propyl   .  .  . 

C3H8O 

96° 

Propionic    . 

C3H602 

140° 

-20°  8 

Butyl  .... 

C4  H100 

109° 

Butyric    .  . 

C4H802 

162° 

— 

Amyl  .... 

C5  H120 

132° 

Valeric  .   .  . 

05  H1002 

174° 

— 

Hexyl.  .  .  . 

C6  H14O 

150° 

Caproic    .  . 

C6  H1202 

199° 

5° 

Heptyl   .  .  . 

C7  H160 

164° 

(Enanthylic 

C7  H1402 

219° 

— 

Octyl  .... 

C8  H180 

196° 

Caprylic  .  . 

C8  H1602 

236° 

16° 

Nonyl  .... 

C9  H200 

— 

Pelargonic  . 

C9  H1802 

254° 

18° 

Decatyl  .  .  . 

C10H220 

212° 

Capric  .  .  . 

C10H2002 

— 

30° 

Hendecatyl  . 

CnH240 

— 

Laurie  .  .  . 

C12H2402 

— 

43.6° 

Dodecatyl    . 

C12H260 

— 

Myristic  .  . 

C14H2802 

— 

53.8° 

Cetyl  .... 

C16H340 

49.5°  2 

Palmitic  .  . 

C16H3202 

— 

62° 



— 

— 

Margaric.  . 

C17H3402 

— 

— 

0  J                   • 

C*    TT    O 

fiQ  9° 







oLcctriO   .     . 

Arachidic    . 

C2oH4*02 



Ut7.^ 

75° 



— 

— 

Behenic   .  . 

C22H4402 

— 

76° 

— 

Hyaenic    .  . 

C25H50O2 

— 

77° 

Ceryl  .... 

C^HgeO 

79°  2 

Cerotic  .  .  . 

C27H5402 

— 

78° 

Myricyl  .  .  . 

C30H620 

85°  2 

Melissic   .  . 

C30H60°2 

— 

88° 

1  So  called  because  some  of  them  occur  in  fats. 

2  Melting-points,  8  Below. 


OXYGEN   DERIVATIVES.  199 

Some  of  the  acids  given  in  the  foregoing  table  occur  in 
well-known  substances.  Butyric  acid  occurs  in  butter. 
Palmitic  acid  occurs  in  many  fatty  compounds,  such  as 
palm  oil,  olive  oil,  and  cocoanut  oil.  Stearic  acid  occurs 
in  such  solid  fats  as  mutton  and  beef  tallow.  These  acids 
are  combined  in  their  natural  fats,  as  palmatin  and  stearin, 
with  an  alcohol  of  the  formula,  C3H8O3,  commonly  called 
glycerine.  Melissic  acid  occurs  in  beeswax. 

229,  Soap.  —  EXP.  98.  Melt  35g  of  cocoanut  or  cotton-seed 
oil  with  18g  of  good  tallow  in  a  large  evaporat ing-dish  or  tin 
basin.  Then  add  a  solution  of  16.5*  of  potassium  hydroxide 
dissolved  in  40CC  of  water.  Heat  the  substances  carefully, 
when  a  chemical  reaction  termed  Saponification  will  soon  ensue. 
The  heat  must  now  be  quickly  removed,  to  prevent  boiling 
over.  When  the  action  ceases,  apply  heat  again,  and  boil 
gently  for  about  fifteen  minutes.  Now  add  about  10s  of  com- 
mon salt,  and  cook  for  thirty  minutes. 

Separate  the  soap  as  completely  as  possible  from  any  "spent 
lye  "  that  may  be  in  the  bottom  of  the  dish,  and  place  the  soap 
in  a  shallow  tin  or  pasteboard  box  to  cool.  Test  the  properties 
of  the  soap  for  cleansing  and  for  making  a  lather. 

When  natural  fats  consisting  of  palmatin,  stearin,  and 
olein  —  a  compound  found  in  many  liquid  oils,  and  con- 
taining oleic  acid,  C^H^O.; —  are  heated  with  an  alkali, 
glycerine  is  set  free,  and  the  fatty  acids  unite  with  the 
metal  of  the  alkali  to  form  salts.  These  salts  constitute 
what  we  call  soap. 

Soaps  may  be  distinguished  as  hard  and  soft  soaps, 
depending  upon  the  fats  and  the  alkalies  which  enter 
into  their  composition.  The  soft  soaps  usually  contain 
cheap  oils,  such  as  ^ard,  fish  oil,  and  house  scraps  (usually 
called  soap  grease}. 


200  OXYGEN   DERIVATIVES. 

Frequently  wood  ashes  are  leached  and  the  potash  lye 
thus  obtained  is  boiled  with  soap  grease,  to  make  soft  soap. 
Cocoanut  oil,  olive  oil,  and  tallow  make  the  best  hard 
soaps.  They  are  usually  combined  with  caustic  soda. 

When  soap  is  brought  in  contact  with  hard  water,  a 
curd  is  formed  which  consists  of  insoluble  calcium  pal- 
mate, stearate,  and  oleate. 

230.  Ethyl  Nitrite,  C2H5N02.  —  It  is  not  necessary  to  notice 
the  remaining  derivatives  of  ethane.  But  there  is  one 
among  the  nitrogen  derivatives,  ethyl  nitrite,  that  is  an 
article  of  commerce.  This  substance  may  be  obtained  by 
adding  potassium  nitrite  to  ethyl  sulphuric  acid :  — 

C2H5HS04  +  KN02  =  C2H5N02  +  HKS04. 

A  solution  of  ethyl  nitrite  in  alcohol  is  sold  in  drug  stores 
as  sweet  spirit  of  nitre,  or  spiritus  cetheris  nitrosi.  It  is 
used  as  a  mild  irritant ;  its  action  on  the  kidneys  is  also 
well  known. 


CHAPTER   XVII. 

A   FEW  DERIVATIVES    OF   THE   ETHYLENE   SERIES   AND   OF 
THE   ACETYLENE   SERIES. 

I.     THE    OLEFINB   DERIVATIVES. 

231.  Ethylene,  C;>H4.  —  This  important  gas  has  already 
been  mentioned  as  forming  the  most  important  constitu- 
ent of  illuminating  gas  produced  by  the  distillation  of  coal. 
In  this  connection  it  is  of  interest  since  it  is  the  lowest 
member  of  the  olefine  series.  The  members  of  this  series 
belong  to  that  class  of  compounds  called  unsaturated  com- 
pounds. They  form  addition  products  in  which  they  act 
like  bivalent  radicals.  The  alcohols,  often  called  G-lycols, 
and  the  acids  are  the  most  important  of  the  olefine  deriva- 
tives. The  alcohols  of  this  series  yield  two  classes  of  acids. 
In  the  first  class,  the  Lactic  Acid  Series,  the  acids  are  mono- 
basic, and  they  are  derived  from  their  corresponding  alco- 
hols by  displacing  two  atoms  of  hydrogen  and  taking  up 
one  atom  of  oxygen.  In  the  second,  or  Oxalic  Acid  Series, 
the  acids  are  dibasic  and  are  derived  from  their  correspond- 
ing alcohols  by  the  displacement  of  four  atoms  of  hydrogen 
and  the  addition  of  two  atonis  of  oxygen.  Among  these 
acids  are  found  some  of  the  best  known  of  the  organic 
acids.  They  occur  quite  widely  distributed  in  nature. 
They  form  well-defined  series  of  salts  with  the  metals, 
some  of  which  are  of  frequent  and  extended  use. 

The  following  table  will  show  the  relations  between  the 
olefine  alcohols  and  their  acids  :  — 

201 


202 


THE   OLEFINE   DERIVATIVES. 


Hydro- 
carbons. 

Alcohols,  or  Glycols. 

Acids  (Monobasic). 

Acids  (Dibasic). 

C2H4 

Ethylene,  C2H4(OH)2 

Glycollic,  C2H403 

Oxalic,  C2H2O4 

C3H6 

Propylene,  C3H6(OH)2 

Lactic,  C3HgO3 

Malonic,  C3H4O4 

C4H8 

Butylene,  C4H8(OH)2 

Butylactic,  C4H803 

Succinic,  C4H6O4 

C6H10 

Amylene,  C5H10(OH)2 

Valerolactic,  C5H1003 

Pyrotartaric,  C3H8O4 

C6H12 

Hexylene,  C6H12(OH)2 

Leucic,  C6H12O3 

Adipic,  C6H1004 

232,  Lactic  Acid,  C3H603,  —  Lactic  acid  occurs  in  sour 
milk,  where  it  is  produced  by  the  action  of  a  lactic  acid 
ferment,  Penicillum  glaucum,  on  the  sugar  of  milk.  It 
also  occurs  in  the  juices  of  vegetables  that  have  turned 
sour.  It  has  not  been  prepared  in  the  anhydrous  condi- 
tion. It  forms  a  series  of  salts  with  the  metals  that  are 
almost  all  uncrystallizable  and  very  deliquescent.  Lactic 
acid  has  two  isomers. 


233,  Oxalic  Acid,  C2H204.  —  This  acid  occurs  as  the  acid 
potassium  salt  in  plants  belonging  to  the  species  known  as 
Oxalis  and  in  other  plants. 

It  can  be  prepared  in  a  variety  of  ways,  but  it  is  now 
prepared  for  commerce  by  heating  pine  sawdust  with  caus- 
tic potash.  Usually  a  mixture  of  caustic  soda  and  caustic 
potash  is  employed  instead  of  the  caustic  potash  alone. 
The  fused  mass  is  treated  with  water,  when  all  but  the 
sodium  oxalate  dissolves.  This  salt  is  ignited  and  then 
treated  with  lime-water,  whereupon  insoluble  calcium  ox- 
alate and  caustic  soda  are  obtained.  From  the  calcium 
oxalate,  oxalic  acid  is  liberated  by  means  of  sulphuric  acid, 
which  gives  insoluble  calcium  sulphate  and  free  oxalic 
acid.  From  the  acid  thus  obtained  in  solution,  crystals 
of  oxalic  acid  are  secured  by  concentration  and  crystalli- 


THE   OLEFINE   DERIVATIVES.  203 

zation.     The  caustic  alkalies  are  regained  and  used  to  act 
upon  more  sawdust. 

Oxalic  acid  is  readily  soluble  in  water  and  in  alcohol, 
and  upon  the  system  it  acts  as  a  poison  when  taken 
in  large  doses.  It  forms,  with  the  metals,  a  series  of 
salts,  the  oxalates,  that  are  used  in  a  variety  of  ways. 
Both  the  acid  and  its  salts  possess  bleaching  properties, 
and  some  of  the  salts  serve  as  useful  reagents  in  the 
laboratory. 

234.  Succinic    Acid,    C4H604.  —  Succinic   acid   occurs    in 
amber   in    certain    lignites    and   in   fossil   wood.     It   also 
occurs  in  such  plants  as  lettuce   and   wormwood.     It  is 
also  one -of  the  products  of  alcoholic  and  acetic  acid  fer- 
mentation. 

Commercial  succinic  acid  is  prepared  by  distilling  amber 
and  by  the  fermentation  of  calcium  malate  and  of  tartaric 
acid. 

235.  Malic  Acid,  C4H605.  —  This  acid  occurs  in  the  juices 
of  fruits,  like  apples,  pears,  gooseberries,  raspberries,  and 
currants.     It  can  best  be  prepared  from  mountain-ash  ber- 
ries or  from  the  stems  and  leaves  of  garden  rhubarb.     The 
juice  is  expressed  and  treated  with  milk  of  lime,  when  in- 
soluble calcium  malate  is  obtained.     This  salt  is  purified, 
and  then  decomposed  by  means  of  sulphuric  acid.     This 
gives  insoluble  calcium  sulphate  and  malic  acid. 

By  comparing  the  formula  of  this  acid  with  that  of  suc- 
cinic acid,  it  will  appear  that  malic  acid  simply  has  one 
atom  more  of  oxygen  than  succinic  acid.  Hence  malic 
acid  is  often  called  oxy-mccinic  acid. 

236.  Tartaric   Acid,    C4H606.  —  This   acid   occurs   widely 
distributed  in  nature.     It  occurs  both  in  the  free   state 


204  THE   OLEFINE   DERIVATIVES. 

and  in  the  form  of  salts  in  many  fruits  along  with  malic 
acid.  Hydrogen  potassium  tartrate  occurs  plentifully 
in  the  juice  of  grapes,  from  which  it  is  deposited  along  with 
the  calcium  salt  during  the  fermentation  of  grape  juice  in 
the  manufacture  of  wine.  The  crude 'salts  thus  obtained 
are  called  "  Argols  "  and  are  employed  in  assaying. 

Tartaric  acid  crystallizes  in  large  transparent  prisms, 
soluble  in  alcohol  and  in  water.  This  acid  finds  many 
uses  in  the  arts,  while  the  hydrogen  potassium  salt, 
KHC4H4O6,  often  called  cream  of  tartar,  is  extensively 
employed  in  the  manufacture  of  baking-powder.  For 
this  purpose  this  salt  is  mixed  with  acid  sodium  carbonate, 
and  a  certain  quantity  of  starch  is  added  as  a  "  filler  "  to 
prevent  chemical  reaction  between  the  other  ingredi- 
ents while  in  a  dry  state.  This  tartrate  finds  other  uses, 
as  in  medicine,  in  silvering,  in  soldering,  and  in  dye- 
ing. Tartar  emetic  has  been  mentioned  under  antimony, 
Art.  137. 

Tartaric  acid  has  two  atoms  of  oxygen  more  than  suc- 
cinic  acid,  whence  the  name  Dioxy-succinic  acid  which  it 
often  bears.  The  acids  of  the  defines  each  have  two  or 
more  isomers  which  are  sometimes  distinguished  by  their 
action  on  polarized  light.  One  may  rotate  the  plane  of 
polarization  to  the  right,  another  to  the  left,  while  perhaps 
a  third  will  be  optically  inactive. 

237.  Citric  Acid.  —  This  acid  belongs  to  a  class  of 
compounds  called  hydroxy  acids,  since  it  contains  a 
hydroxyl  group,  as  appears  from  the  rational  formula, 
C3H3(OH)(CO2H)3.  It  is  a  tribasic  acid,  yielding  both 
acid  and  normal  salts. 

It  occurs  widely  distributed  in  nature  like  malic  and  tar- 
taric  acids.  It  is  obtained  for  commerce  from  lemon  juice. 


THE   OLEFINE   DERIVATIVES.  205 

The  juice  is  allowed  to  ferment,  lime  is  added,  and  the 
calcium  citrate  thus  obtained  is  then  purified,  and  after- 
wards treated  with  sulphuric  acid. 

It  is  also  found  in  the  orange,  cranberry,  and  whortle- 
berry. With  about  an  equal  quantity  of  malic  acid  it 
occurs  in  the  currant,  gooseberry,  strawberry,  cherry,  and 
raspberry,  and  berries  of  the  mountain-ash. 

This  acid  is  much  used  in  preparing  lemonade  and  other 
cooling  drinks.  It  also  is  used  in  medicine,  in  calico- 
printing,  and  in  dyeing.  Of  its  salts,  magnesium  citrate, 
Mg3(C6H5O7)2  +  14  H2O,  made  by  dissolving  magnesia, 
MgO,  in  citric  acid,  is  used  in  medicine  as  a  mild  pur- 
gative. Effervescing  citrate  of  magnesia  is  made  by  add- 
ing to  this  salt  citric  acid,  acid  sodium  carbonate,  and 
sugar.  The  whole  is  then  moistened  with  alcohol  and 
afterwards  dried. 


238,  Glycerine,  Glycerol,  or  Propenyl  Alcohol, 
—  Glycerine,  as  will  appear  from  its  formula,  is  a  triad  alco- 
hol containing  three  hydroxyls.  This  is  the  best-known 
compound  of  its  class.  In  comparing  with  propylene, 
C3H6,  it  appears  that  not  only  are  the  two  combining 
equivalents  of  propylene  satisfied  with  hydroxyls,  but 
also  one  hydrogen  is  replaced  by  a  hydroxyl. 

Glycerine,  as  already  mentioned,  occurs  in  most  of  the 
fats  from  which  it  can  be  separated  by  saponification.  It 
can  also  be  isolated  by  treating  the  natural  fats  with  super- 
heated steam  ;  and  it  is  in  this  way  that  a  larger  part  of 
the  glycerine  of  commerce  is  prepared. 

Glycerine  is  a  syrupy,  odorless  liquid  of  a  sweetish. 
pleasant  taste.  It  is  readily  soluble  in  alcohol  and  in 
water,  but  insoluble  in  ether  and  chloroform.  It  is  much 
used  in  pharmaceutical  preparations,  for  manufacturing 


206  ACETYLENE   DERIVATIVES. 

copying-ink,  for  "improving"  liquors,  and,  owing  to  the 
ease  of  its  digestibility,  for  a  food. 

But  perhaps  the  largest  consumption  of  glycerine  is  for 
the  manufacture  of  the  powerful,  high-grade,  explosive 
nitro-glycerine,  C3H5(NO2)3.  This  compound  is  made  by 
treating  one  part  of  glycerine  with  a  mixture  consisting 
of  four  parts  of  sulphuric  acid  and  one  part  of  nitric  acid, 
at  a  low  temperature.  The  nitre-glycerine  separates  out 
as  an  oily  liquid,  and  it  must  be  carefully  freed  from  acids 
to  prevent  its  decomposition,  which  is  frequently  accom- 
panied by  terrific  explosions.  But  at  its  best  the  liquid  is 
not  safe  to  handle.  Consequently  it  is  now  mostly  used 
in  the  form  of  dynamite  or  giant  powder*  These  substances 
are  prepared  by  allowing  absorbent  substances  like  Kiesel- 
guhr,  a  siliceous  kind  of  earth,  to  take  up  the  liquid.  In 
this  form  nitro-glycerine  is  much  used  in  blasting.  It  is 
usually  exploded  by  percussion. 


239.  Oleic  Acid,  C^H^.  —  This  acid  occurs  in  most  of 
the  liquid  fats  and  many  solid  fats  combined  with  glycer- 
ine.     It  is  obtained  in  large  quantities  as  a  by-product 
in  manufacturing  stearin  candles.     A  crude  form  of  this 
acid  containing  other  fatty  acids  may  be  had  by  dissolving 
castile  soap  in  water,  and  then  treating  the  solution  with 
hydrochloric  acid. 

II.     ACETYLENE   DERIVATIVES. 

240.  Linoleic  Acid,  C^H^O^.  —  Acetylene  has  been  men^ 
tioned  in  Art.  82.     Of   the  derivatives  belonging  to  the 
acetylene  series  we  shall  notice  but  one  or  two. 

Linoleic  acid  occurs  combined  with  glycerine  as  trilin- 
olein  in  linseed  oil.     It  is  to  this  compound  that  linseed 


ACETYLENE   DERIVATIVES.  207 

(flaxseed)  oil  owes  its  value  as  an  ingredient  of  paints. 
When  a  thin  layer  of  linseed  oil  is  exposed  to  the  air, 
oxygen  is  taken  up,  and  the  glycerine  is  oxidized,  leaving 
a  gummy  mass  behind  which  is  little  acted  upon  by  heat 
or  moisture.  For  the  same  reasons  linseed  oil  is  much 
used  in  the  manufacture  of  varnishes. 

241.  Mannite,  or  Mannitol,  C6H8(OH)6. — Just  as  glycerine 
is  a  triad  alcohol,  so  is  niannite  a  hexad  alcohol.  This  sub- 
stance occurs  in  manna,  the  dried  sap  of  certain  species  of 
ash,  as  Fraxinus  ornus  and  F.  rotundifolia.  It  also  occurs 
in  many  other  forms  of  vegetation,  as  in  the  roots  of  celery, 
in  the  sugar-cane,  in  olives,  and  in  many  fungus-like 
plants. 

The  manna  mentioned  in  the  Bible  contained  no  man- 
nite,  but  instead  a  kind  of  sugar.  It  was  probably  the 
dried  sap  of  a  species  of  Tamarix.  The  manna  mentioned 
as  falling  from  heaven  may  have  been  a  kind  of  lichen, 
Spcerothallia  esculenta,  which  is  carried  about  by  the 
winds. 

There  is  an  isomer  of  mannite  which  is  called  Dulcite. 
Both  these  substances  possess  a  sweetish  taste,  and  are 
more  closely  related  to  the  carbohydrates  of  the  next 
chapter  than  to  any  other  class  of  compounds. 


CHAPTER   XVIII. 

THE  CARBOHYDRATES. 

242,  Carbohydrates  is  a  term  applied  to  a  class  of  carbon 
compounds  containing  hydrogen  and  oxygen  in  the  same 
proportion  as  found  in  water.  These  substances  seem  to 
be  closely  allied  to  the  hexad  alcohols,  but  the  exact  rela- 
tions are  not  very  clearly  defined. 

For  convenience  of  consideration  the  carbohydrates  may 
be  divided  into  three  classes :  — 

1.  The  Sucroses,  C^H^On,  embracing  cane  sugar,  milk 
sugar,  maltose,  etc. 

2.  The  G-lucoses,  C6H12O6,  embracing  grape  sugar,  levu- 
lose,  etc. 

3.  The   Amyloses,    (CeHuAX,1   including    starch,  dex- 
trine, gums,  cellulose,  etc. 

These  compounds  are  of  the  greatest  importance.  They 
occur  widely  distributed  throughout  the  vegetable  king- 
dom, and  they  play  an  important  part  in  the  nourishment 
and  growth  of  both  plants  and  animals.  The  sucroses  and 
glucoses  are  sweet  to  the  taste  and  freely  soluble  in  water. 
The  amyloses  are  generally  tasteless  and  insoluble  in  water. 
The  first  two  classes  are  remarkable  for  their  power  of  ro- 
tating the  plane  of  polarized  light.  Cane  sugar,  milk  sugar, 
maltose,  and  grape  sugar  rotate  the  plane  to  the  right  (+), 
while  levulose  rotates  it  to  the  left  (— ). 

1  This  formula  indicates  that  the  molecular  formulas  are  not  exactly 
determined. 

208 


THE   SUCROSES.  209 

Again,  many  of  these  compounds  possess  the  property  of 
reducing  solutions  of  cupric  salts  to  cuprous  oxide.  Upon 
the  two  properties  last  named  the  methods  employed  for 
the  quantitative  determination  of  the  sugars  are  based. 
Thus  cane  sugar  is  determined  by  its  dextro-rotary  power, 
specially  constructed  apparatus  being  employed,  while 
glucose  is  estimated  by  its  reducing  effect  on  Fehling's 
solution,  an  alkaline  solution  of  copper  sulphate,  Rochelle 
salts,  and  sodium  hydroxide. 

THE   SUCROSES. 


243,  Sucrose,  or  Cane  Sugar,  CvfLzfin>  —  This  is  the  best 
known  of  all  the  sugars.  It  is  of  wide  distribution,  and  is 
prepared  for  commerce  in  enormous  quantities.  The  prin- 
cipal sources  of  cane  sugar  are  the  sugar  beet,  the  sugar- 
cane, the  sugar  maple,  and  sorghum.  Until  recently  the 
sugar-cane  furnished  the  larger  part  of  the  sugar  of  com- 
merce ;  but  recent  estimates  now  accredit  that  honor  to 
the  sugar  beet.  The  sugar  beet  contains  from  eight  to 
twenty  per  cent  of  cane  sugar  and  the  sugar-cane  from 
fourteen  to  twenty.  In  exceptional  cases  the  percentages 
for  both  have  been  known  to  exceed  twenty  per  cent. 

There  have  been  many  processes  employed  in  manufac- 
turing sugar.  The  simplest  of  these  is  the  one  employed 
in  making  maple  sugar.  An  incision  is  made  in  the  tree, 
and  just  beneath  is  fastened  a  spile  or  spout  which  carries 
the  sap  into  a  trough  or  bucket  placed  at  the  foot  of  the 
tree.  At  intervals  the  sap  is  collected  and  carried  to  large 
kettles  or  pans  that  are  frequently  placed  in  the  sugar 
forest  at  some  convenient  location.  These  kettles  are  often 
placed  in  the  open  air,  and  are  heated  by  means  of  direct 
fires.  Here  the  sap  is  evaporated,  and  any  scum  that  rises 


210  THE   SUCROSES. 

is  simply  skimmed  off.  When  the  sap  reaches  a  syrupy 
consistence,  it  is  removed  from  the  large  kettles,  and  the 
"sugaring  off"  is  completed  in  smaller  kettles,  very  fre- 
quently on  the  kitchen  stove.  In  this  latter  process  the 
concentration  is  carried  on  till  the  sugar  will  grain  on 
cooling,  when  it  is  placed  in  pans  or  tins  and  allowed  to 
cool.  It  is  now  ready  for  market. 

Of  late  many  improvements  have  been  introduced  into 
the  manufacture  of  sugar  from  sugar  beets  and  sugar-cane. 
That  known  as  the  "  diffusion  process  "  is  by  all  means  the 
best.  In  this  process  the  canes  or  beets  are  first  cut  into 
thin  slices,  or  sometimes  in  the  case  of  beets  they  are  torn 
into  shreds.  Now  by  the  judicious  application  of  hot 
water  the  sugar  diffuses  through  the  cell  walls  of  the 
plants,  leaving  behind  most  of  the  uncrystallizable  im- 
purities. In  order  to  accomplish  this  end,  a  series  of 
from  twelve  to  sixteen  boiler-iron  cylinders  or  "  cells " 
are  arranged  in  a  circle  to  form  what  is  termed  a  "bat- 
tery." 

These  cells  are  first  filled  with  the  chips,  and  then 
a  charge  of  hot  water  and  steam  is  introduced  into 
No.  1.  From  here  the  water  is  next  forced  into  No.  2, 
and  then  into  No.  3,  and  so  on  around.  When  the 
last  cell  is  reached  the  water  has  taken  up  sugar  from 
every  cell  until  it  is  now  a  somewhat  concentrated  sugar 
solution. 

It  will  readily  be  understood  that  the  chips  in  the  first 
cell  where  the  water  was  pure  have  lost  more  sugar  than 
the  chips  in  any  of  the  succeeding  cells ;  also  that  as  the 
water  passed  along  from  cell  to  cell  it  gradually  took  less 
and  less  sugar,  so  that  the  chips  in  the  last  cell  were  ex- 
hausted least  of  all.  From  the  last  cell  the  concentrated 
solution  is  run  into  a  large  liming-tank,  and  a  fresh  charge 


THE   SUCROSES.  211 

of  water  is  started  in  again  at  No.  1  and  passed  around  as 
before. 

Other  charges  of  water  are  then  introduced  into  No.  1 
and  passed  around  until  the  chips  in  that  cell  are  ex- 
hausted. Then  these  chips  are  removed  and  fresh  ones 
are  introduced.  Now  the  next  charge  of  fresh  water  is 
started  at  No.  2,  and  finally  taken  out  at  No.  1.  Then 
fresh  chips  are  placed  in  No.  2,  and  the  next  charge  of 
water  is  started  at  No.  3  and  taken  out  at  No.  2 ;  and  thus 
the  process  is  continued. 

When  the  liming-tank  is  filled,  it  is  heated,  and  lime  is 
added  to  remove  impurities.  From  this  tank  the  juice  is 
passed  into  another,  where  the  excess  of  lime  is  removed 
by  means  of  carbon  dioxide.  If  necessary,  the  juice  is  next 
filtered  through  boneblack  filters,  from  which  it  is  passed 
into  vacuum  pans,  where  it  is  concentrated  until  the  crys- 
tal] izing-point  is  reached.  The  crystals  are  removed  and 
dried  in  centrifugal  driers.  By  further  concentration  a 
second  and  even  a  third  crop  of  crystals  may  be  obtained, 
when  nothing  is  left  excepting  uncrystallizable  molasses. 
The  molasses  from  beet  sugar  is  much  used  for  manufac- 
turing alcohol. 

Raw  sugars  from  the  cane  and  from  beets  are  usually 
sent  to  the  refiners,  where  the  remaining  impurities  are 
removed,  and  the  sugar  worked  up  in  a  variety  of  ways 
ready  for  the  market. 

France  and  Germany  now  produce  most  of  the  beet 
sugars  of  the  world.  This  industry  now  bids  fair  to 
become  established  in  the  United  States. 

Cane-sugar  crystals  obtained  by  slow  evaporation  are 
large  and  transparent,  but  when  the  crystals  are  formed 
rapidly,  they  are  small,  striated,  and  nearly  opaque.  Water 
at  45°  dissolves  nearly  two  and  a  half  times  its  weight  of 


212  THE   SUCROSES. 

cane  sugar.    When  fused  at  about  175°  for  some  time,  sugar 
is  changed  into  a  mixture  of  levulosan  and  dextrose :  — 

C^H^On  =  C6H1005  -{•  C6H1206. 

When  heated  to  higher  temperatures  a  substance  called 
Caramel  is  produced.  When  submitted  to  still  higher  tem- 
peratures, or  when  treated  with  concentrated  sulphuric 
acid,  sugar  is  decomposed,  oxygen  and  hydrogen  in  the 
proportions  found  in  water  are  removed,  and  carbon  is 
left  behind. 

EXP.  99.  Dissolve  2g  or  3g  of  sugar  in  about  the  same 
quantity  of  water,  and  while  the  solution  is  warm  slowly  add 
concentrated  sulphuric  acid.  Note  the  remaining  carbon. 

When  sugar  in  water  solution  is  strongly  heated  or  ex- 
posed to  the  action  of  dilute  acids,  or  of  certain  other 
reagents,  it  is  changed  into  "  invert  sugar,"  which  is  Isevo- 
rotary,  and  which  consists  of  a  mixture  of  equal  parts  of 
levulose  and  dextrose  :  — 

C12H22On  -f-  H20  =  C6H1206  -f-  C6H1206. 

In  alcoholic  fermentation  the  ferment  first  changes  the 
sugar  into  invert  sugar,  after  which  the  conversion  into 
alcohol  proceeds  by  the  further  action  of  the  ferment  on 
the  invert  sugar.  Cane  sugar  of  itself  is  not  fermentable. 

244.  Milk  Sugar,  Lactose,  C12H22On.  —  Milk  sugar  is  an 
isomer  of  cane  sugar,  which  occurs  in  the  milk  of  the 
Mammalia,  and  of  which  it  constitutes  about  four  per 
cent.  This  sugar  is  said  to  occur  in  but  one  plant,  a 
tree,  Sapota  achras,  a  native  of  the  West  Indies. 

Commercial  milk  sugar  is  prepared  from  milk  whey, 
which  is  simply  concentrated  and  allowed  to  stand  in  a 
cool  place  until  the  sugar  separates  out  in  crystals.  Some- 


THE   GLUCOSES.  213 

times  the  crystallization  is  aided  by  suspending  strings  in 
the  whey.  As  found  in  commerce,  milk  sugar  usually  con- 
sists of  elongated  crystalline  masses  containing  one  equiv- 
alent of  water.  It  is  hard  and  gritty,  and  is  not  very 
sweet  to  the  taste.  It  is  employed  in  medicine. 

When  the  sugar  in  milk  ferments,  it  yields  lactic  acid 
and  alcohol.  The  lactic  acid  coagulates  the  albumen 
of  the  milk,  and  thus  causes  the  milk  to  thicken. 

Maltose  is  also  an  isomer  of  cane  sugar,  which  is  pre- 
pared by  the  action  of  malt  on  starch.  There  are  several 
other  isomers  of  cane  sugar  which  are  of  less  importance. 

THE  GLUCOSES. 

245.  Grape  Sugar,  Dextrose,  or  Glucose,  C6H1:i06.  —  Grape 
sugar  occurs  widely  distributed  in  plants  along  with  equal 
parts  of  levulose,  the  two  forming  invert  sugar.  Some 
cane  sugar  is  usually  present  at  the  same  time.  Grape 
sugar  also  occurs  in  honey,  but  it  is  most  plentiful  in  the 
sweet  juices  of  ripe  fruits  such  as  grapes,  cherries,  etc. 

This  sugar  is  called  dextrose,  owing  to  its  dextro-rotary 
action  on  polarized  light. 

Under  the  name  of  Glucose  grape  sugar  is  now  manufac- 
tured in  enormous  quantities  by  heating  starch  with  water 
containing  from  one  to  two  per  cent  of  sulphuric  acid. 

EXP.  100.  To  100CC  of  water  in  a  flask  add  lcc  of  sulphuric 
acid,  and  boil.  Slowly  add  to  the  contents  of  the  flask,  without 
checking  the  boiling,  10g  of  starch  which  have  been  made  into 
a  paste  with  water.  Boil  for  three  hours.  Then  add  powdered 
chalk  or  marble  until  the  acid  is  completely  neutralized,  and 
then  filter.  Finally  evaporate  the  filtrate  to  a  thick  syrup, 
and  then  set  it  away  in  a  cool  place.  Note  the  taste,  and  from 
time  to  time  examine  the  solution  for  crystals  of  glucose. 


214  THE   AMYLOSES. 

The  preceding  experiment  illustrates  in  a  general  way 
the  process  employed  in  manufacturing  glucose.  Glucose 
is  now  extensively  used  in  the  manufacture  of  candy  and 
syrups  and  for  the  adulteration  of  cane  sugar.  It  is 
cheaper  than  cane  sugar,  and  is  not  so  sweet.  Unless 
properly  purified  it  contains  some  substances  which  act 
upon  the  system  like  the  pernicious  fusel  oil  found  in 
impure  alcoholic  liquors. 

EXP.  101.  Test  samples  of  sugar,  candy,  and  syrups  for 
glucose,  thus :  First  prepare  one-half  litre  of  Fehling's  solu- 
tion as  follows  :  Dissolve  17.32g  pure  copper  sulphate  in  a 
small  quantity  of  water,  and  then  add  100s  of  Rochelle  salts 
(sodium  potassium  tartrate).  Then  add  ahout  300CC  of  a  solu- 
tion of  sodium  hydroxide  of  a  specific  gravity  1.12.  Then 
dilute  to  one-half  litre  by  adding  pure  water. 

Now  place  about  10CC  of  the  clear  blue  solution  thus  pre- 
pared in  a  large  test-tube,  and  boil.  While  still  boiling  add  a 
few  drops  of  a  water  solution  of  the  substance  to  be  tested,  and 
continue  the  boiling  for  a  short  time.  Then  add  a  few  drops 
more  of  the  same  solution,  and  boil  as  before.  If  the  Fehling's 
solution  loses  color,  add  more  of  the  substance  to  be  tested, 
and  boil.  Continue  this  process  until  the  color  is  destroyed. 
Now  allow  the  solution  to  stand  a  short  time,  and  if  a  reddish 
precipitate  of  cuprous  oxide  collects  in  the  tube,  glucose  is  pres- 
ent. Cane  sugar  has  no  reducing  effect  on  the  copper  solution. 

Levulose,  which  has  already  been  mentioned  several  times, 
occurs  with  dextrose  in  fruits,  etc.  It  it  a  Isevo-rotary  iso- 
mer'of  dextrose  that  does  not  crystallize.  It  is  nearly  as 
sweet  as  cane  sugar. 

THE    AMYLOSES. 

246.  Starch,  or  Amylum,  (C6H1005),(,  —  Starch  occurs  in 
nearly  every  part  of  most  growing  plants,  and  especially  of 


THE   AMYLOSES.  215 

those  plants  containing  chlorophyll.  It  is  formed  from  the 
protoplasm  which  the  chlorophyll  cells  contain.  But  the 
largest  deposits  are  to  be  found  in  seeds,  grains,  tubers, 
bulbs,  and  piths,  where  the  starch  is  stored  away  to  fur- 
nish material  for  the  next  season's  growth.  Some  biennial 
and  perennial  plants  make  deposits  of  starch  in  their 
thickened  leaves  for  the  same  purpose. 

EXP.  102.  Agitate  about  100g  of  wheat  bran  with  sufficient 
water  to  form  a  thin  paste.  Filter  through  a  linen  cloth,  using 
pressure  if  necessary.  Allow  the  filtrate  to  stand  for  some 
time.  Test  the  white  sediment  that  is  deposited  for  starch,  by 
moistening  a  part  of  it  with  a  dilute  solution  of  iodine  in  potas- 
sium iodide  solution.  If  starch  be  present,  it  will  turn  blue. 
Moisten  a  second  portion  of  the  sediment  with  a  dilute  solution 
of  potassium  iodide,  and  then  examine  it  with  a  microscope 
magnifying  from  200  to  300  diameters.  Similarly  prepare  and 
test  starch  from  corn  and  potatoes.  Also  examine  the  pith  of 
growing  twigs  of  trees  for  starch. 

Starch  is  prepared  for  commerce  from  a  variety  of  sub- 
stances, such  as  corn,  wheat,  arrow-root,  and  potatoes.  In 
one  of  the  common  processes  employed,  the  starch  is  washed 
out  of  the  moistened  and  finely  divided  substance  by  means 
of  water,  after  which  it  is  allowed  to  ferment  in  order  to 
destroy  some  of  the  impurities  present.  Finally,  it  is 
washed  in  pure  water  by  decantation. 

The  grains  of  starch  exhibit  under  the  microscope  pecul- 
iar markings  and  forms  which  differ  according  to  the  source 
from  which  the  starch  was  obtained.  Thus  the  microscope 
is  able  to  reveal  the  origin  of  any  sample  of  starch  as  well 
as  to  expose  any  adulteration.  The  markings  are  more 
clearly  brought  out  by  treating  the  starch  with  dilute 
potassium  hydroxide  solution. 


216  THE   AMYLOSES. 

The  largest  grains  of  starch  occur  in  the  potato,  while 
the  smallest  are  found  in  rice. 

When  starch  is  heated  to  205°,  it  is  converted  into  an 
isomer  termed  Dextrine.  This  is  much  used  as  a  substitute 
for  gum  arabic.  The  backs  of  postage  stamps  and  the 
flaps  of  envelopes  are  gummed  with  dextrine. 

When  the  starch  is  moistened  with  a  mixture  of  dilute 
hydrochloric  and  nitric  acids,  the  conversion  into  dextrine 
takes  place  at  from  100°  to  125°.  In  fact,  most  of  the  dex- 
trine of  commerce  is  prepared  in  this  way. 

247.  The  Gums,  (C6H1005)n.  —  Of  the  gums,  gum  arabic 
and   gum    tragacanth   are    well-known    examples.      Gum 
arabic  exudes  from  several  species  of  acacias,  which  are 
natives  of  tropical  regions.     These  gums  are  used  for  mak- 
ing mucilage,  confectionery,  and  inks,  and  for  many  phar- 
maceutical purposes. 

Nearly  every  kind  of  wood  and  vegetable  tissue  carries' 
gummy  substances,  which  are  usually  soluble  in  water. 

248,  Cellulose,  (C6H1005)n.  —  Cellulose  occurs  in  all  plants, 
since  it  forms  the  basis  of  all  cell-walls.     But  it  seldom 
occurs  pure,  as  some  of  the  solids  which  the  sap  carries  in 
solution  are  deposited  in  the  cell-walls  during  the  growth 
of  the  tissues. 

Cellulose  is  of  great  importance,  since  it  forms  the  bulk 
of  many  fibres  which  are  used  in  enormous  quantities. 
Among  these  fibres  may  be  mentioned  cotton,  hemp,  flax, 
and  wood  fibres  which  are  extensively  used  for  making 
cloth,  cordage,  paper,  etc. 

Gun-Cotton,  or  cellulose  hexnitrate,  C12H14(NO3)6O10,  is  a 
powerful  explosive  prepared  by  first  treating  cotton  wool 
with  alkalies  to  remove  gummy  matters,  after  which  it  is 


ui  IYER  SIT  y 


THE   AM 

treated  with  a  mixture  of  strong  nitric  and-ffBftpfiOnc  acids. 
Finally,  it  is  washed  with  much  pure  water  until  every 
trace  of  free  acid  is  removed  in  order  to  prevent  sponta- 
neous decomposition,  which  is  often  accompanied  by  disas- 
trous explosions.  ' 

Collodion  is  a  solution  of  some  of  the  lower  nitrates  of 
cellulose  in  a  mixture  of  alcohol  and  ether.  It  is  used  in 
surgery  and  in  photography. 

249.  The  Glucosides.  —  Under  this  name  are  included  a 
number  of  substances  occurring  in  plants.  On  decompo- 
sition they  yield  a  glucose  together  with  other  substances. 

Amygdalin,  C^H^NOu-fEIIaO,  occurs  in  bitter  almonds, 
apple  seeds,  peach  pits,  etc. 

Salicin,  C]3H18O7,  is  found  in  the  bark  of  willows,  and 
in  the  bark  and  leaves  of  poplars. 

The  Tannins  occur  in  the  barks  of  certain  trees,  but 
more  especially  in  the  gall-nuts  found  on  oak-trees.  The 
tannins  have  the  property  of  forming  inks  with  ferric  salts. 
They  are  largely  used  for  that  purpose,  and  for  tanning 
leather. 


CHAPTER  XIX. 

THE     TERPENES,     BENZENES,    STYRENES,    NAPHTHALENES, 
AND  ANTHRACENES,   AND  THEIR   DERIVATIVES. 

THE   TERPENES,    CnH2n_4. 

250,  The  Terpenes,  C10H16.  —  Of  this  series  of  hydrocar- 
bons, the  turpentines,  the  camphors,  and  certain  essential 
oils  are  among  the  best-known  compounds. 

Turpentine,  C10H16,  is  the  product  of  southern  pine-trees, 
Pinus  australis.  Turpentine  is  also  obtained  in  some 
parts  of  Europe.  A  tree  is  wounded,  and  the  pitch  which 
oozes  out  is  allowed  to  collect  in  a  box  or  pocket  which  is 
cut  into  the  tree.  In  France  a  vessel  is  used  to  collect  the 
pitch.  From  time  to  time  the  pitch  is  gathered  up  until 
a  sufficient  quantity  has  been  collected,  when  it  is  sub- 
jected to  distillation.  The  turpentine  distils  over,  and  the 
solid  residue  is  sold  under  the  name  Rosin. 

Ex.     State  the  uses  of  turpentine. 

When  turpentine  is  acted  upon  by  hydrochloric  acid,  a 
peculiar  substance  called  Artificial  Camphor,  C10H16HC1, 
is  produced.  This  substance  closely  resembles  camphor. 

Camphor,  or  Laurinol,  C10H16O,  is  obtained  by  distilling 
with  water  chips  of  Laurus  camphora,  a  tree  growing  in 
China  and  Japan. 

Borneo  Camphor,  C10H16O,  occurs  in  Dryolalanops  cam- 
phora, a  tree  native  to  Borneo  and  the  adjacent  islands. 

218 


THE   BENZENES.  219 

Belonging  to  the  terpene  series  are  a  large  number  of 
essential  oils  that  occur  in  various  parts  of  different  plants. 
Among  these  oils  those  of  lemon,  bergamot,  neroli,  mace, 
sassafras,  bay,  anise,  fennel,  peppermint,  spearmint,  laven- 
der, and  rosemary  may  be  mentioned  as  consisting  princi- 
pally of  terpenes. 

Closely  allied  to  the  terpenes  is  Caoutchouc,  or  Indian 
Rubier,  which  consists  of  the  dried  milky  juice  of  the 
Jatropha  elastica  and  other  kindred  plants. 

Vulcanized  rubber  contains  from  twelve  to  fifteen  per 
cent  of  sulphur,  and  is  prepared  by  heating  caoutchouc 
with  sulphur  to  about  150°.  At  higher  temperatures  Vul- 
canite or  Ebonite  is  obtained. 

G-utta  Percha  is  the  dried  juice  of  a  tree,  Isonandra 
percha,  a  native  of  the  East  Indies. 

THE   BENZENES,    CnH2n_6. 


251.  Benzene,  CeHe.  —  This  series  is  often  called  the 
Aromatic  Series,  since  several  fragrant  compounds  belong 
to  it.  The  lowest  known  term  is  Benzene  (not  the  com- 
mercial benzine,  which  is  a  mixture  of  paraffin  hydrocar- 
bons), or,  as  it  is  sometimes  called,  Benzol. 

Coal  tar  has  been  mentioned  as  one  of  the  by-products 
in  the  manufacture  of  illuminating  gas  ;  and  it  is  from  this 
source  that  benzene  is  chiefly  obtained.  The  crude  tar  is 
subjected  to  fractional^  distillation.  The  "  first  runnings," 
which  include  all  products  boiling  under  110°,  contain 
small  quantities  of  benzene.  The  "light  oil,"  however, 
coming  over  between  110°  and  210°  contains  benzene  in 
larger  quantities.  From  this  light  oil  benzene  is  separated 
and  purified  by  further  fractional  distillation  and  by  treat- 
ment with  sulphuric  acid  and  caustic  soda. 


220  THE   BENZENES. 

Benzene  is  a  colorless,  strongly  refracting  liquid,  pos- 
sessing a  characteristic  odor,  and  burning  with  a  luminous 
but  smoky  flame.  It  boils  at  80.5°.  It  serves  as  an  excel- 
lent solvent  for  various  fats,  resins,  alkaloids,  etc.,  and  it 
is  extensively  used  in  the  manufacture  of  the  aniline  dyes. 
Benzene  forms  both  substitution  and  addition  products  ; 
but  in  all  these  compounds  all  six  carbon  atoms  appear. 
Various  facts  noted  in  the  chemical  behavior  of  benzene 
have  led  to  the  adoption  of  a  graphical  formula  in  which 
the  carbon  atoms  are  arranged  in  the  form  of  a  ring  or 
closed  chain,  the  carbons  being  connected  alternately  with 
one  and  two  linkages.  This  formula  may  be  represented 
as  follows  :  — 

H 
I 

C 
H-CX  ^C-H 


H-C 


I 
H 


Now  the  substitution  products  of  benzene  are  made  by 
replacing  one  or  more  of  the  hydrogens,  leaving  the  carbons 
undisturbed. 

In  the  best  known  of  the  addition  products,  benzene  acts 
like  a  hexad  radical,  thus  :  benzene  hexchloride,  C6H6C16  ; 
benzene  hexbromide,  C6H6Br6.  To  account  for  these  com- 
pounds, the  supposition  has  been  made  that  one  of  each  of 
the  double  links  has  been  broken,  thus  giving  up  six  bonds 
to  new  uses. 

Since  any  one  or  all  of  the  hydrogens  of  benzene  may 
be  replaced  by  a  radical  ;  and  further,  since  the  hydrogens 
of  these  substituted  radicals  may  be  replaced  by  elements 


THE   BENZENES.  221 

or  radicals  ;  and  again,  since  each  compound  may  have  sev- 
eral isomers,  it  is  evident  that  the  derivatives  to  be  obtained 
from  benzene  are  simply  innumerable. 

Of  the  homologous  series  of  which  benzene  is  the  first 
member,  four  members  are  known  :  — 

Benzene  ........  C6H6. 

Toluene  ........  C7H8. 

Xylene  ........  C8H10. 

Cyinene  ......     .     . 


We  can  here  notice  only  a  few  of  the  most  important 
compounds  derived  from  this  series. 


252.  Phenol,  Phenyl  Alcohol,  or  Carbolic  Acid, 
Phenol,  although  a  true  alcohol  corresponding  to  the 
hydrocarbon  benzene,  is  quite  generally  known  as  carbolic 
acid.  It  is  prepared  from  that  fractional  distillation  prod- 
uct of  coal  tar  which  boils  between  150°  and  200°.  The 
"middle  oil"'  obtained  between  these  temperatures  is 
treated  with  caustic  soda  and  afterward  with  sulphuric 
acid. 

Now  since  phenol  forms  a  hydrate  with  water  which 
splits  up  into  the  pure  acid  and  water  upon  distillation, 
this  reaction  is  used  for  the  final  purification  of  the  better 
grades  of  carbolic  acid. 

Phenol  possesses  a  characteristic  odor,  is  soluble  in 
water,  and  when  taken  internally  it  is  a  violent  poison. 
It  is  much  used  as  a  disinfectant. 

Phenol  forms  a  well-defined  series  of  derivatives,  among 
which  is  trinitrophenol,  or  Picric  Acid,  C^H^NOg^OH. 
Picric  acid  is  a  very  bitter  poisonous  substance  which  is 
used  alone  for  dyeing  silk  and  woollen  goods  yellow. 
With  other  dyes  it  is  used  for  producing  different  shades. 


222  THE   BENZENES. 

Picric  acid  is  now  manufactured  by  the  action  of  nitric 
acid  on  phenolsulphonic  acid,  C6H4(OH)SO3H,  although 
it  is  to  be  had  by  the  use  of  phenol  and  nitric  acid. 

253,  Resorcin  and  Pyrogallol.  —  It  will  be  noticed  that 
phenol  is  a  monad  alcohol,  but  just  as  one  would  expect 
there  are  other  benzene   alcohols.     Resorcin,  C6H4(OH)2, 
is  a  diad  alcohol  obtained  by  melting  various  resins  with 
caustic  potash.     It  is  largely  used  in  manufacturing  dyes. 

Pyrogallol,  or  Pyrogallic  Acid,  C6H3(OH)3,  is  a  triad 
alcohol  obtained  by  subliming  gallic  acid  at  from  210° 
to  220°.  It  is  found  in  commerce  as  lustrous,  flaky,  or 
acicular  crystals.  It  is  used  as  a  reagent  in  gas  analy- 
sis on  account  of  the  ease  and  rapidity  with  which  it 
absorbs  oxygen.  It  is  also  used  in  photography  as  a 
developer. 

254.  Nitrobenzene,   C6H5N02,  —  Nitrobenzene   is   a  light 
yellow,  strongly  refracting  liquid  which  has  an  odor   re- 
sembling the  oil  of  bitter  almonds  somewhat  modified  by 
another  odor  suggesting  oil  of  cinnamon. 

It  is  manufactured  in  large  quantities  under  the  name 
of  artificial  oil  of  bitter  almonds  or  essence  of  mirbane. 
It  is  prepared  by  treating  benzene  with  a  mixture  of  strong 
nitric  and  sulphuric  acids.  The  'crude  oil  is  purified  by 
passing  through  it  a  current  of  steam,  after  which  it  is 
treated  with  caustic  soda  and  distilled  with  steam  under 
pressure. 

Although  nitrobenzene  is  somewhat  poisonous,  and  has 
an  irritating  effect  on  the  skin,  nevertheless  it  is  used  in 
perfuming  the  cheaper  grades  of  soap.  But  the  largest 
quantities  are  employed  in  the  manufacture  of  aniline, 
aniline  blue,  aniline  black,  and  magenta. 


THE   BENZENES.  223 


255.  Aniline,  Amidobenzene,  or  Phenylamine, 

Aniline  is  now  manufactured  in  enormous  quantities  for 
use  in  preparing  the  aniline  dyes.  It  is  obtained  by  the 
action  of  nascent  hydrogen  on  nitrobenzene.  The  nitro- 
benzene is  placed  in  a  large  iron  cylinder  fitted  with  a 
stirring  apparatus,  and  the  hydrogen  is  furnished  by  add- 
ing directly  to  it  hydrochloric  acid  and  iron.  The  crude 
product  is  purified  by  distillation. 

Aniline  is  a  colorless  liquid  of  a  characteristic  odor  and 
possessing  strong  basic  properties.  It  forms  definite  salts 
with  the  ordinary  acids,  and  together  with  its  compounds 
it  is  invaluable  to  the  color  industry.  It  acts  upon  the 
system  as  a  powerful  poison. 

256.  The  Toluenes.  —  Toluene,  C7H&  is  obtained  by  dis- 
tilling toluic  acid  with  an  excess  of  lime.     It  occurs  natu- 
rally in  petroleum,  and  can  be  obtained  by  various  reactions 
upon  benzene. 

The  Cresols,  C7H8O,  of  which  there  are  three  isomers, 
occur  in  coal  tar,  pine  tar,  and  creosote. 

The  toluene  alcohol,  C7H7OH,  is  called  Benzyl  Alcohol. 
It  occurs  in  balsam  of  Peru  and  in  balsam  of  Tolu. 

The  aldehyde  of  benzyl  alcohol,  C7H8O,  or  benzoic  alde- 
hyde, is  the  true  Oil  of  Bitter  Almonds.  It  occurs  in  a 
glucoside,  amygdalin,  one  of  the  constituents  of  bitter 
almonds,  cherry  pits,  laurel  leaves,  etc.  Under  the  influ- 
ence of  emulsin,  a  ferment  found  in  amygdalin  itself, 
amygdalin  breaks  up  into  glucose,  prussic  acid,  and  oil 
of  bitter  almonds  :  — 

CaHjyNOu  +  2  H20  =  2  CeHjA  +  HCN  +  C7H60. 

Benzoic  aldehyde  on  oxidation  passes  into  Benzoic  Acid, 
C7H6O2,  a  monobasic  acid  occurring  in  gum  benzoin  and 


224  THE   BENZENES. 

the  balsams  of  Peru  and  Tolu.  It  also  occurs  in  the  urine 
of  herbivorous  animals.  Benzoic  acid  may  be  obtained  in 
a  variety  of  ways,  but  the  best  commercial  article  is  ob- 
tained by  subliming  gum  benzoin.  Cheaper  forms  are 
prepared  from  the  urine  of  cows  and  horses,  and  by  the 
oxidation  of  toluene. 

EXP.  103.  Place  a  small  quantity  of  benzoic  acid  in  a 
beaker  with  no  lip,  and  then  fit  a  paper  funnel  over  the  mouth 
of  the  beaker.  Place  the  apparatus  on  the  sand-bath  and  heat 
gently.  Note  the  sublimate  of  benzoic  acid  which  collects 
inside  the  funnel. 

Salicylic  Acid,  C7H6O3,  occurs  as  methyl  salicylate  in  oil 
of  wintergreen,  from  which  it  is  prepared  for  commercial 
purposes.  It  is  also  prepared  by  treating  benzene  with 
caustic  soda  and  carbon  dioxide.  Salicylic  acid  is  now 
largely  used  as  an  anti-ferment  and  in  medicine. 

G-allic  Acid,  C7H6O5,  occurs  in  many  plants,  such  as 
sumach,  Chinese  tea,  and  in  nut-galls.  It  is  prepared 
from  nut-galls  by  the  fermentation  of  the  tannin  which 
they  contain. 

Tannic  Acid,  C14H10O,  also  occurs  in  nut-galls,  from 
which  it  is  obtained  for  commerce. 

Nitrotoluene,  C7H7NO2,  is  prepared  by  treating  toluene 
with  nitric  acid.  By  reduction  with  hydrogen  this  sub- 
stance is  reduced  to  Amidotoluene,  C7H7NH2,  which  is  a 
necessary  constituent  of  the  red  and  violet  aniline  colors. 
This  substance  occurs  as  an  ingredient  of  commercial 
aniline. 

There  are  three  isomeric  Xylenes,  C8H10,  all  to  be  ob- 
tained from  coal  tar.  Cymene,  C9Hi2,  occurs  in  oil  of  cara- 
way and  in  oil  of  thyme.  It  can  be  prepared  from  the 
terpenes. 


THE   STYRENES,    OB   CINNAMINES.  225 

Closely  related  to  the  benzene  derivatives  is  the  common 
substance  known  as  Indigo.  The  indigo  plants  are  natives 
of  tropical  countries.  From  them  indigo  is  prepared  by 
placing  the  plants  in  tanks  and  covering  them  with  water. 
Fermentation  sets  in,  and  when  it  is  completed  the  water 
solution  is  drawn  off,  carrying  the  coloring-matter  in  solu- 
tion. Upon  standing,  the  indigo  is  precipated,  when  it  is 
collected,  pressed,  and  dried  ready  for  the  market.  The 
value  of  indigo  depends  upon  the  amount  of  Indigo  Blue, 
or  Indigotin,  C16H10N2O2,  which  the  crude  article  contains. 
Indigo  is  now  prepared  artificially. 

THE    STYRENES,    OR   CINN  AMINES,    CnH2n_8. 

257.  Styrene,  or  Cinnamine,  C^S.8.  -  -  This  hydrocarbon 
occurs  in  liquid  storax,  a  fragrant,  honey-like  substance 
which  yields  styrene  upon  distillation  with  water  and 
sodium  carbonate. 

Styryl  alcohol,  C9H10O,  belongs  to  this  series,  and  its  al- 
dehyde, cinnamic  aldehyde,  C9H8O2,  constitutes  the  greater 
part  of  the  essential  oil  of  cinnamon.  Cinnamic  acid, 
C9H8O2,  closely  resembles  benzoic  acid.  It  occurs  in  storax 
and  in  balsam  of  Peru.  This  acid  is  now  manufactured  on 
the  large  scale  by  treating  benzyl  chloride,  C7H6Cl2,  with 
sodium  acetate. 


THE   NAPHTHALENES,    CnH2n_ 


1-2- 


258.  Naphthalene,  C10H8.  —  This  hydrocarbon  occurs  in 
large  quantities  in  the  heavier  portions  of  coal  tars, 
boiling  between  180°  and  220°.  It  crystallizes  in  large 
pearly  plates.  From  careful  studies  of  the  chemical 
behavior  of  naphthalene  it  has  been  discovered  that  this 
hydrocarbon  consists  of  two  benzene  residues  which  con- 


226  THE  ANTHRACENES. 

tain  two  carbons   in    common.      The   following   formula 
will  show  its  constitution  :  — 

H          H 

I  I 

C1  0* 

H-C^    XCX    ^C-H 

I  II  I 

H-C          0       ^C-H 

^C/    ^C^ 

I        I 

H          H 

Naphthalene,  C10H8. 

Naphthalene  forms  many  derivatives,  and  among  them 
are  some  of  the  most  beautiful  dyes.  Thus  Martius'  Yel- 
low, C10H5OH(NO2)2,  Naphthol  Yellow  S.,  K2C10H4N2SO8, 
and  other  splendid  colors  belong  to  this  series. 

THE   ANTHRACENES,    CnH2n_i8. 

259.  Anthracene,  C14H10.  —  Anthracene  is  prepared  from 
those  portions  of  coal  tar  boiling  between  340°  and  360°. 
It  crystallizes  in  white,  silky  scales  or  plates,  and  like 
naphthalene  it  furnishes  beautiful  dyes.  Its  constitution 
is  exemplified  by  the  following  formula :  — 

H  H 

I  I 

C          H          C 

//    \        I        /    % 
H-C  C-C-C  C-H 

I  II      I      II  I 

H-C  C-C-C  C-H 

%    /  I        \    // 

C  H          C 

I  I 

H  H 

Anthracene,  CHH,0. 


THE   ANTHRACENES.  227 

Among  the  dyes  derived  from  anthracene  we  may  men- 
tion Alizarin,  C14H8O4,  and  Purpurin,  C14H8O5.  These 
substances  are  found  naturally  in  madder  root,  which 
has  been  used  from  the  earliest  times  as  the  source 
of  a  red  dye.  Formerly  large  tracts  of  land  were  devoted 
to  the  cultivation  of  the  madder  plant,  but  now  Turkey 
Red,  as  this  dye  is  called,  is  nearly  all  obtained  from 
coal  tar. 


CHAPTER   XX. 

THE  ALKALOIDS   AND   THE  ALBUMINOIDS. 

260,  The  term  Alkaloids  is  applied  to  a  class  of  sub- 
stances contained  in  a  large  variety  of  plants,  and  espe- 
cially those  containing  medicinal  and  poisonous  principles. 
Our  knowledge  of  the  constitution  and  relations  of  these 
substances  is  extremely  limited,  and  in  most  cases  entirely 
wanting. 

The  alkaloids  are  optically  active  on  polarized  light; 
some  being  dextro-rotary,  and  some  being  Isevo-rotary.  In 
their  chemical  behavior  they  resemble  the  amines  and  the 
amides ;  and  they  all  contain  carbon,  hydrogen,  and  nitro- 
gen, and  nearly  all  contain  oxygen. 

They  are  nearly  all  crystallizable,  especially  those  that 
are  solids  ;  and  they  form  crystallizable  salts  with  the 
ordinary  acids. 

Conine,  C8H15N,  the  active  principle  of  poison  hemlock, 
and  Nicotine,  C10H14N2,  the  active  poison  found  in  tobacco, 
are  liquids.  These  are  among  the  most  important  of  the 
liquid  alkaloids. 

Caffeine,  C8H10N4O2,  is  found  in  tea  and  coffee,  and  in 
other  plants  that  are  used  to  prepare  infused  beverages. 
Theobromine,  C7H8N4O2,  is  found  in  cocoa. 

Opium,  the  dried  sap  of  certain  species  of  poppies,  fur- 
nishes about  nineteen  different  alkaloids,  which  possess 
more  or  less  active  properties.  Among  the  more  note- 
worthy are  Morphine,  C17H19NO3 .  H2O ;  Codeine,  C18H21NO3 ; 
228 


THE   ALKALOIDS   AND   THE  ALBUMINOIDS.  229 

Thebaine,  C19H21NO3;  and  Narcotine,  C^H^NO,.  The  sul- 
phates of  these  alkaloids  are  most  used. 

Cinchona  bark  furnishes  about  twenty-one  alkaloids,  of 
which  Quinine,  C^K^NgO,,,  and  Cinchonine,  C^H^^O,  are 
the  most  important.  The  sulphates  and  chlorides  of  these 
alkaloids  find  extended  use. 

Nux  vomica  furnishes  the  powerful  poisons,  Strychnine, 
enHaNA,  and  Brucine,  C^HJSTA  •  4  H2O. 

The  reader  is  referred  to  any  of  the  standard  works  on 
pharmacy,  or  to  the  dispensatories,  for  lists  and  descrip- 
tions of  the  crude  drugs  and  alkaloids  used  in  medicine. 

261.  The  Albuminoids  are  compounds  of  very  complex 
constitution,  concerning  which  our  knowledge  is  quite 
incomplete.  They  do  not  crystallize,  but  exist  in  an 
amorphous,  jelly-like  form ;  and  in  consequence  it  is 
nearly  impossible  to  obtain  them  in  a  state  of  sufficient 
purity  to  enable  us  to  determine  with  exactitude  the  pro- 
portions in  which  their  constituents  unite,  or  even  to  be 
certain  what  elements  are  present  in  the  pure  compounds. 

Nevertheless,  these  compounds  are  of  great  importance 
to  both  plants  and  animals.  In  plants  they  occur  in  nearly 
every  part,  but  more  especially  in  the  seeds.  In  young 
and  growing  plants,  particularly  those  used  as  food  for 
man  and  animals,  the  albuminoids  are  quite  generally  dis- 
tributed throughout  the  tissues. 

G-luten  is  the  albuminoid  found  in  grains,  and  is  a  sticky, 
elastic  substance  which  gives  tenacity  to  dough. 

Albumen  is  found,  in  the  purest  form,  in  the  whites  of 
eggs.  This  substance  may  be  obtained,  as  a  flocculent 
precipitate,  by  adding  acetic  acid  to  the  white  of  an  egg, 
and  then  diluting  with  water.  Albumen  also  occurs  in  the 
serum  of  blood. 


230  THE   ALKALOIDS   AND   THE   ALBUMINOIDS. 

Fibrin  may  be  obtained  from  fresh  blood  by  whipping  it 
with  a  bundle  of  twigs.  Fibrin,  when  thus  obtained,  and 
after  washing  with  water,  appears  in  the  form  of  whitish 
threads,  which  are  tasteless  and  insoluble  in  water.  Fibrin 
remains  in  solution  while  the  blood  is  circulating  through 
its  proper  channels ;  but  on  removing  the  blood  from  the 
circulation,  the  fibrin  immediately  causes  coagulation. 

Casein  is  the  albuminoid  found  in  milk,  and  separates 
out  as  curd  when  the  milk  becomes  sour. 

The  albuminoids  possess  in  common  the  property  of 
coagulating,  upon  the  application  of  heat,  or  by  con- 
tact with  alcohol.  They  readily  undergo  putrefaction, 
and  in  other  respects  their  resemblances  are  close. 

They  all  contain  sulphur,  and  many  of  them  contain 
phosphorus,  beside  carbon,  nitrogen,  hydrogen,  and  oxy- 
gen. No  formula  can,  with  certainty,  be  assigned  to 
albumen. 


INDEX. 

(INORGANIC  AND  ORGANIC.) 

[The  numbers  refer  to  pages.] 


Absolute  alcohol 192 

Acetic  acid 196 

Acetone 197 

Aceto-nitril 186 

Acetylene 61,  72 

Acids 59 

Acid  salts 61 

Addition  products 173 

Agate 92 

Albumen 229 

Albuminoids 30,  229 

Alizarin 227 

Alkalies,  "  Fixed  " 31 

"Volatile" 31 

Alkaloids 228 

Alloys 101 

Aluminum 138 

Occurrence  and  preparation,  138 
Properties  and  compounds,  138 

Tests 140 

Aluminum  bronze 139 

Aluminum  hydroxide 139 

Aluminum  sulphate 139 

Aluminum  trioxide 138 

Alums 139 

Anfalgams 101 

Amido  benzene 227 

Amines 185 

Ammonia,  Occurrence 30 

Preparation  and  properties,     31 
Tests..  33 


Ammonium 161 

Salts  of 162 

Amorphous  phosphorus 95 

Amygdalin 217 

Amyloses 208 

Amylum 214 

Analysis  of  an  unknown 163 

Aniline 223 

Anthracene 226 

Anthracite 67 

Antimony 118 

Occurrence  and  preparation,  118 

Properties  and  compounds,  118 

Tests 119 

Antimony  acids 119 

Antimony  oxides 119 

Antimonyl  salts 118 

Antimony  trisulphide 119 

Arabs 1 

Argillaceous  iron  ore 132 

Argols 204 

Aromatic  series 219 

Arsenic 114 

Occurrence  and  preparation,  114 

Properties  and  compounds,  115 

Tests 116 

Arsenic  acid .115,  116 

Arsenic  pentoxide 116 

Arsenic  trioxide 116 

Arsenious  acid 116 

Arsenious  sulphide 116 

231 


232 


INDEX. 


Arsines 187 

Artificial  camphor 218 

Asbestos 153 

Asphalt 179 

Asphaltum 179 

Atomic  theory 8 

Atomic  weights 8 

Atoms 7 

Aqua  ammonise 31 

Aqua  regia 47 

Avogadro's  hypothesis 38 

Baking-powder 75 

Barium 149 

Occurrence  and  preparation,  149 

Properties  and  compounds,  149 

Tests 150 

Barium  carbonate 149 

Barium  chloride 149 

Barium  hydroxide 149 

Barium  oxide 149 

Barium  sulphate 149 

Baryta 149 

Baryta  water 149 

Bases 60 

Basic  salts 61 

Beet  sugar 209 

Benzene 219 

Benzoic  acid 223 

Benzol 219 

Benzyl  alcohol 223 

Beryl 139 

Binary  compounds 57 

Bismuth 122 

Occurrence  and  preparation,  122 

Properties  and  compounds,  122 

Tests 123 

Bismuth  nitrate 123 

Bismuth  ochre 122 

Bismuth  trioxide 123 

Bismuth  trisulphide 123 


Bismuthite 122 

Bismuthyl  nitrate 123 

Bismuthyl  salts 123 

Bituminous  coal 67 

Black  diamonds 68 

Blanc  de  farcl 123 

Blanc  d'Espagne 123 

Bleaching-powder .48,  152 

Bog  iron  ore 132 

Bohemian  glass 161 

Boneblack 66 

Borneo  camphor 218 

Boron,  Occurrence. 93 

Tests 94 

Brass 144 

Brimstone 79 

Bromic  acid 51 

Bromine,  Occurrence 50 

Preparation 50 

Test 50 

Bromine  oxacids 51 

Brucine 229 

Butyric  acid 199 

Cacodyl  compounds 188 

Cadmium 125 

Occurrence  and  preparation,  125 

Tests 126 

Cadmium  iodide 126 

Cadmium  sulphide 126 

Caffeine 228 

Calcium 151 

Occurrence  and  preparation,  151 

Properties  and  compounds,  152 

Tests 153 

Calcium  carbonate 151^  153 

Calcium  chloride 152 

Calcium  hydroxide  152 

Calcium  oxide , 152 

Calc  spar 152 

Calomel  .  .110 


INDEX. 


233 


Camphor 218 

Cane  sugar 209 

Caoutchouc 80,  219 

Caramel 212 

Carbamides 186 

Carbamines 186 

Carbinol 193 

Carbohydrates 208 

Carbolic  acid 221 

Carbon,  Occurrence 65 

Preparation  and  properties,     65 

Tests 69 

Carbonado 68 

Carbon  dioxide,  Occurrence. . .     72 
Preparation  and  properties,     73 

Tests 75 

Carbon  disulphide 89 

Carbon  monoxide 72 

Carbonylamines 186 

Casein 230 

Cassiterite 120 

Cast  iron 134 

Celestine 150 

Cellulose 216 

Cellulose  hexnitrate 216 

Chalcedony 92 

Charcoal 65,  66 

Chemical  affinity 10 

Chemism 10 

Chemistry,  Origin  of 1 

Chert 92 

Chili  saltpetre 158 

China  clay 138 

Chloric  acid 48 

Test 49 

Chloral 196 

Chloral  hydrate 196 

Chlorine,  Occurrence. 43 

Preparation  and  properties,     43 

Test 43 

Chlorine  oxacids. .  48 


Chlormethane 180 

Chloroform 180 

Chlorous  acid, 48 

Chrome  alum 137 

Chrome  ironstone 137 

Chrome  yellow 106,  137 

Chromic  oxide 137 

Chromium,  Occurrence,  etc 137 

Tests 138 

Cinchona  bark 229 

Cinchonine 229 

Cinnabar 79 

Cinnamic  acid 225 

Cinnamic  aldehyde 225 

Cinnamine 225 

Citric  acid 204 

Clay 92 

Clay  ironstone 132 

Coal 65,  67 

Coal  tar 71,  219 

Cobalt 141 

Occurrence  and  preparation,  141 
Properties  and  compounds,    142 

Tests 142 

Cobalt  glance 141 

Cobalt  oxide 142 

Cobaltous  chloride 142 

Cobaltous  nitrate 142 

Cobaltous  sulphide  142 

Codeine 228 

Coke 71 

Collodion 217 

Combining  number 9 

Compounds 7 

Condensation  of  vapors 39 

Condy's  disinfecting  fluid  ....  143 

Conine 228 

Copper 124 

Occurrence  and  preparation,  124 

Tests 125 

Copper  aceto-arsenite 116 


234 


INDEX. 


Copper  arsenite 116 

Copper  sulphate 125 

Corals 152 

Corrosive  sublimate 110 

Cosmoline 178 

Cresols 223 

Crocoisite 137 

Crystallization 15 

Cyanic  acid 186 

Cyanogen 186 

Cyamiric  acid 186 

Cymene 221,  224 

Cymogene 178 

Decantation 3 

Determination  of  atomic  weights,  63 
Determination  of  molecular 

weights 37 

Determination  of  valence 64 

Dextrine 216 

Dextrose 212,  213 

Diamond  drills 68 

Diamond  dust 68 

Diamonds   65,  67,  68 

Dibasic  acids 84 

Diffusion  batteries 210 

Diffusion  of  gases 22 

Diffusion  process 210 

Dimethylamine 185 

Dioxy-succinic  acid 204 

Dog-tooth  spar 152 

Dolomite 153 

Dryobalanops  camphora 218 

Dulcite 207 

Dulong  and  Petit' s  law 101 

Dutch  liquid 71 

Dynamite 206 

Ebonite 81,  219 

Electrolysis 24 

Elements  denned  . .  4 


Elementals  and  derivatives. . . .   171 

Elixir  vitse 1 

Equations 56 

Ethane 69,  189 

Ethyl  alcohol 189 

Ethyl  aldehyde 196 

Ethylene..... 71,201 

Ethyl  ether 194 

Ethyl  nitrate 200 

Evaporation 2 

Experimentation ....       1 

Experiment  denned 2 

Fehling's  solution 214 

Feldspar 92,  138 

Fermentation 73 

Ferric  chloride 135 

Ferric  hydroxide 135 

Ferrous  sulphate 135 

Ferrous  sulphide 135 

Fibrine 230 

Fifth  group  metals 103,  156 

Filtration 3 

Fire  damp 70 

First  group  metals 101,  104 

First  runnings 219 

Flashing-point 179 

Flint 92 

Flowers  of  sulphur 79 

Fluorine 53 

Fool's  gold 79,  132 

Formic  acid 184 

Formic  aldehyde 184 

Fourth  group  metals 103,  155 

Fractional  distillation 191 

Franklinite  144 

Fulminating  powder 187 

Fusible  metals 122 

Galena 79,  104 

Gallic  acid  . .  .224 


INDEX. 


235 


Gas  carbon * 67 

Gasoline 178 

Gaultheria  procumbens 182 

Giant  powder 206 

Glacial  acetic  acid 197 

Glass 161 

Glucose 213 

Glucoses 208 

Glucosides 217 

Glycerine ^  . . .  205 

Glycerol 205 

Gluten 229 

Gold 128 

Grape  sugar 213 

Graphite 65,  67,  134 

Guignet's  green 137 

Gums 216 

Gun-cotton 40,  216 

Gunpowder 40,  159 

Gutta  percha 219 

Gypsum 79,  152 

Hematite 132 

Halogen  derivatives 172 

Heavy  spar 79 

Higher  compounds 59 

Homologous  series 169 

Homology 169 

Hone  stone 92 

Hydracids 59 

Hydriodic  acid 53 

Tests 53 

Hydrobromic  acid 51 

Hydrocarbons 170 

Hydrochloric  acid 46 

Test 47 

Hydrocyanic  acid 76,  186 

Hydrogen 19 

Test 22 

Hydrogen  sulphide 81 

Tests, .  82 


Hydroxylamine 187 

Hypobroinous  acid 51 

Hypochlorous  acid 48 

Hyponitrous  acid 38 

Hypophosphorous  acid 97 

Hyposulphurous  acid 84 

Iceland  spar 151 

Illuminating  gas 71 

Indian  rubber 219 

Indigo 225 

Indigo  blue 225 

Indigotin 225 

Invert  sugar 212 

lodic  acid 53 

Iodine 51 

Tests 52 

Iodine  pentoxide 53 

lodoform 181 

Iron 132 

Properties  and  compounds,  135 

Tests 136 

Iron  furnace 133 

Iron  pyrites 79,  132 

Iron  slag 134 

Isocyanides 186 

Isomerism 174 

Isomers 175 

Isonandra  percha 219 

Isonitroso  compounds 187 

Jatropha  elastica 219 

Kaolin 138 

Kelp 52 

Kerosene 178 

Ketones 197 

Kupfer  nickel 140 

Lac  sulphuris 80 

Lactic  acid..  .  202 


236 


INDEX. 


Lactic  acid  series 201 

Lactose 212 

Lampblack 65 

Laurinol 218 

Lauras  camphora 218 

Law  of  definite  proportions  ...  8 

Law  of  multiple  proportions  . .  36 

Lead 104 

Properties  and  compounds,  105 

Tests 106 

Lead  acetate 106 

Lead  chloride 106 

Levulosan 212 

Levulose 214 

Light  oil. 219 

Lignite 67 

Lime-kilns 152 

Linoleic  acid1 206 

Litharge 105 

Lodestone 132 

Lubricating  oil 178 

Lunar  caustic 108 

Magnesia 154 

Magnesite 153 

Magnesium ....  153 

Tests 154 

Magnesium  carbonate 154 

Magnesium  chloride 154 

Magnesium  sulphate 153,  154 

Malic  acid 203 

Manganese 142 

Tests 143 

Manganese  dioxide 143 

Maganese  sulphide 143 

Manganic  acid 143 

Manna 207 

Mannite 207 

Mannitol 207 

Maple  sugar 209 

Marble...  .  152 


Marsh  gas 70 

Martius'  yellow 226 

Massicot 105 

Meerschaum 153 

Melissic  acid 199 

Mercaptans 187 

Mercuric  chloride 110 

Mercury 109 

Tests Ill 

Mercurous  chloride 110 

Mercurous  nitrate 110 

Metallic  derivatives 188 

Metals,  Introduction . . . , 100 

Metals  of  the  alkalies 156 

Metals  of  the  alkaline  earths . .   148 

Metameric  isomers 175 

Methane. 69,  180 

Methyl  alcohol 182 

Methyl  aldehyde 184 

Methylamine 185 

Methyl  ether 183 

Methyl  chloride 180 

Methyl  mercaptan 187 

Methyl  salicylate 182 

Mica 92 

Middle  oil 221 

Milk  of  sulphur 80 

Milk  sugar 212 

Mispickel 114 

Molecular  formulae 10 

Molecules '    9 

Monobasic  acids 84 

Morphine 228 

Naphtha 178 

Naphthaline 225 

Naphthol  Yellow  S 226 

Narcotine 229 

Natural  gas 70 

Nickel 140 

Tests..  .   141 


INDEX. 


237 


Nicotine 228 

Nitric  acid 39 

Tests 41 

Nitrils 186 

Nitrobenzene 222 

Nitro-compounds 187 

Nitrogen 29 

Nitrogen  derivatives 172 

Nitrogen  monoxide 35 

Tests 36 

Nitrogen  oxacids 38 

Nitro-glycerine 40,  206 

Nitro- hydrochloric  acid 47 

Nitro-inethane 186 

Nitrous  acid 38 

Nordhausen  or  fuming  sulphuric 

acid 89 

Normal  salts 61 

Nux  vomica 229 

Oil  of  bitter  almonds 223 

Oil  of  wintergreen 182 

Olefiant  gas 69 

Olefine  acids  and  alcohols 202 

Oleic  acid 206 

Opal 92 

Opium 228 

Organic  chemistry 168 

Organic  substances 168 

Oriental  amethyst 138 

Oriental  emerald 138 

Oriental  topaz 138 

Orpiment 114 

Orthoclase 156 

Orthosilicic  acid 92 

Oxacids 59 

Oxalic  acid 202 

Oxalic  acid  series 201 

Oxides  of  chlorine 48 

Oxides  of  nitrogen 34 

Oxides  of  phosphorus 97 


Oxygen 12 

Tests 17 

Oxygen  derivatives. 172 

Oxysuccinic  acid 203 

Ozone 16 

Palmitic  acid 199 

Paraffin 178 

Paraffin  series 176 

Paris  green 116 

Peat 67 

Penicillum  glaucuui 202 

Pentathionic  acid 84 

Perbromic  acid 51 

Perchloric  acid 48 

Periodic  acid 53 

Permanganic  acid 143 

Petroleum 177 

Phenol 221 

Phenylamine 223 

Philosopher's  stone 1 

Phosphine 96 

Phosphines 187 

Phosphoric  acid 97 

Phosphorous  acid 98 

Phosphorus 94 

Picric  acid 221 

Pinus  australis 218 

Plastic  sulphur 80 

Platinum 129 

Polymeric  isoiners 175 

Porcelain  clay 138 

Potash 159 

Potassium 156 

Properties  and  compounds,  157 

Tests 159 

Potassium  bichromate 137 

Potassium  carbonate 159 

Potassium  chlorate 158 

Potassium  ferrocyanide 136 

Potassium  ferricyanide 136 


238 


INDEX. 


Potassium  hydroxide 158 

Potassium  iodide 158 

Potassium  nitrate , . . .  158 

Potassium  permanganate 143 

Potassium  sulphate 156 

Precipitation 2 

Propenyl  alcohol 205 

Proteids 30 

Prussic  acid 76 

Purpurin 227 

Pyrogallic  acid 222 

Pyrogallol 222 

Pyrolusite 142 

Qualitative  analysis 103 

Quantitative  analysis 103 

Quartz 92 

Quartzite 92 

Quicklime 152 

Quinine 229 

Red  fire 150 

Red  oxide  of  mercury 109 

Red  phosphorus 95 

Reduction 3 

Resorcin 222 

Rhigoline 178 

Rinmann's  green 145 

Roll  sulphur 79 

Rosin 218 

Ruby 138 

Safety  lamp 70 

Salicin 217 

Salicylic  acid 224 

Salt 159 

Saltpetre 156,  158 

Salts 60 

Sand 92 

Sandstone 92 

Sapota  achras 212 


Sapphire 138 

Scheele's  green 116 

Schweinfurth's  green 116 

Secondary  alcohols 192 

Second  group  metals 102,  114 

Separation  of 126 

Separation  of  first  group  metals,  111 
Separation  of  third  group  metals, 

145 

Shells 152 

Silica 92 

Siliceous  conglomerates 92 

Silicon 92 

Tests 93 

Silver 106 

Properties  and  compounds,  107 

Tests 107 

Silver  chloride 108 

Silver  nitrate 108 

Silver-plating  solution 108 

Skutterudite 141 

Smalt 142 

Smithsonite 144 

Soap 197 

Soda-water 95 

Sodium 159 

Properties  and  compounds,  160 

Test 161 

Sodium  aluminate 139 

Sodium  carbonate 160 

Sodium  stannate 121 

Soft  coal 67 

Solution 163 

Solution  of  gases 31 

Soot 65 

Speiss  cobalt 141 

Spirits  of  hartshorn 33 

Spiritus  setheris  nitrosi 200 

Stannic  acid 121 

Stannic  sulphide 121 

Stannous  sulphide 121 


INDEX. 


239 


Starch 214 

Stearic  acid 199 

Steel 134 

Stibines 187 

Stibnite 118 

Stone  coal 67 

Stream  tin 120 

Strontianite 150 

Strontium 150 

Tests 151 

Strontium  nitrate 150 

Strychnine 227 

Styrene 225 

Styryl  alcohol 225 

Subnitrate  of  bismuth 123 

Substituted  ammonias 185 

Substituting  power  and  valence,  63 

Substitution 172,  173 

Succinic  acid 203 

Sucrose 209 

Sucroses 208 

Sugar  manufacture 210,  211 

Sulphonic  acids 188 

Sulphur 79 

Tests 81 

Sulphur  derivatives 172 

Sulphur  dioxide 83 

Tests 84 

Sulphur  trioxide 83,  84 

Sulphuric  acid 84,  85 

Preparation  and  properties,     86 

Tests 89 

Sulphurous  acid 84,  85 

Sylvite 156 

•Synthesis 24 

Symbols 7 

Table  of  elements 5,  6 

Table  of  primary  hydrocarbons,  170 
Table  of  primary  paraffin  alco- 
hols and  acids 198 


Tannic  acid 224 

Tannins 217 

Tartar  emetic 119 

Tartaric  acid 203 

Tellurium 90 

Terpenes 218 

Tertiary  alcohols 194 

Tetrabasic  acids 84 

Tetrathionic  acid 84 

Thebaine 229 

Theobromine 228 

Thiosulphuric  acid 84 

Test 89 

Third  group  metals. ......  102,  131 

Tin 120 

Tin,  Properties  and  compounds,  121 

Test 121 

Tin  stone 120 

Toluene ; 221 

Toluenes 223 

Topaz 139 

Tribasic  acids 84 

Trichlor-rnethane 180 

Tri-iodo- methane 181 

Trimethylamine 185 

Trithionic  acid 84 

Turf 67 

Turkey  red 227 

Turpentine 218 

Turquoise 138 

Uniformity  of  derivatives 175 

Unsaturated  radicals 174 

Urea 186 

Valence 62 

Vaselene 178 

Ventilation 77 

Vinasses 176,  182,  185 

Vinegar 196 

Vulcanite  81,  219 


240 


INDEX. 


Water 23 

White  lead 105 

Willemite 144 

Witherite 149 

Wood  alcohol 182 

Wrought  iron 134 

Xylenes 221,  224 


Zinc 144 

Tests 145 

Zinc  blende 144 

Zinc  chloride 144 

Zinc  ethyl  188 

Zinc  methyl 188 

Zinc  sulphide 145 

Zinc  white  . .  .144 


ENGLISH  LANGUAGE. 


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SCIENCE. 

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of  Carbon.     For  students  of  the  pure  science,  or  its  application  to  arts.    $1.30. 


S   Laboratory    Manual.      Containing  directions  for  a  course  of  experiments 
in  Organic  Chemistry,  arranged  to  accompany  Remsen's  Chemistry.     Boards.     40  cts.  ' 

Coit's  Chemical  Arithmetic.  With  a  short  system  of  Elementary  Qualitative 
Analysis  For  high  schools  and  colleges.  60  cts. 

Grabfield  and  Burns'  Chemical  Problems.    For  preparatory  schools.  60  cts. 

Chute's  Practical  PhysiCS.  A  laboratory  book  for  high  schools  and  colleges  study- 
ing physics  experimentally.  Gives  free  details  for  laboratory  work.  $1.25. 

Colton's  Practical  Zoology.  Gives  a  clear  idea  of  the  subject  as  a  whole,  by  the 
careful  study  of  a  few  typical  animals.  90  cts. 

Boyer's  Laboratory  Manual  in  Elementary  Biology.    A  guide  to  the 

study  of  animals  and  plants,  and  is  so  constructed  as  to  be  of  no  help  to  the  pupil  unless 
he  actually  studies  the  specimens. 

Clark's  Methods  in  MicrOSCOpy.  This  book  gives  in  detail  descriptions  of  methods 
that  will  lead  any  careful  worker  to  successful  results  in  microscopic  manipulation.  $1.60. 

Spalding's  Introduction  tO  Botany.  Practical  Exercises  in  the  Study  of  Plants 
by  the  laboratory  method,  go  cts. 

Whiting's  Physical  Measurement.  Intended  for  students  in  Civil,  Mechani- 
cal and  Electrical  Engineering,  Surveying,  Astronomical  Work,  Chemical  Analysis,  Phys- 
ical Investigation,  and  other  branches  in  which  accurate  measurements  are  required. 

I.     Fifty  measurements  in  Density,  Heat,  Light,  and  Sound.     $1.30. 
II.     Fifty  measurements  in  Sound,   Dynamics,   Magnetism,    Electricity.     $1.30. 
III.     Principles  and  Methods  of  Physical  Measurement,  Physical  Laws  and  Princi- 

ples, and  Mathematical  and  Physical  Tables.     $1.30. 

IV.  Appendix  for  the  use  of  Teachers,  including  examples  of  observation  and  re- 
duction. Part  IV  is  needed  by  students  only  when  working  without  a  teacher,. 
$1.30. 

Parts  I-III,  in  one  vol.,  $3.25.     Parts  I-IV,  in  one  vol.,  $4.00. 

Wllliams's  Modern  Petrography.  An  account  of  the  application  of  the  micro- 
scope to  the  study  of  geology.  Paper.  25  cts. 

For  elementary  -works  see  our  list  of  booksinElementary  Science. 


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